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Shelleys midterm
Earth science midterm
| Question | Answer |
|---|---|
| Fiords are found exclusively along the coast of Norway. | False |
| Gravity plays an important role in all mass wasting events. | True |
| The velocity of a river usually increases downstream. | True |
| Which of the following statements are true about deserts? | despite infrequent rainfalls, erosional and depositional features of running water are important in desert landscapes |
| Which of the following best describes how geysers erupt? | water slowly boils in a network of vertical cracks above the water table, sending up a plume of steam and hot water. |
| Hot springs are most numerous in which region of the United states? | West |
| is an irregular, usually thin till layer laid down by a retreating glacier. | Ground moraine |
| Loess consists mainly of silt-sized particles. | True |
| A is likely to host a waterfall or steep rapids today. | Hanging valley |
| A stream pattern is developed only on growing mountains like volcanoes or where the land surface is tectonically doming upward. | Radial |
| The downstream end or snout of a glacier advances over periods of time during which ablation exceeds accumulation. | False |
| A stream begins at an elevation of 200 meters and flows a distance of 400 kilometers to the ocean. What is the average gradient? | .5m/km |
| A___________represents a former meltwater channel or tunnel in glacial ice that was filled with sand and gravel. | esker |
| Which of the following features characterize wide streams and valleys? | Natural levees; broad floadplains |
| Crevasses are short, narrow cracks in the plastic flow zone of a glacier that alternately open and close as the ice flows along. | False |
| The source of heat for most hot springs is hot igneous material beneath the surface. | True |
| During the most recent ice age, glaciers covered about________percent of Earth's land area. | 30 |
| More water is evaporated from the ocean than is returned to the ocean by precipitation. | True |
| The Basin and Range region of the western United states is an excellent example of a mountainous desert landscape. | True |
| Rapid surge movements of the Earth's tectonic plates offer a convincing explanation for the advances and retreats of the Pleistocene ice sheets. | False |
| A broad accumulation of stratified drift deposited adjacent to the downstream edge of an end moraine is a | outwash plain |
| The transfer of rock material down slope under the influence of gravity is termed | mass wasting |
| A fiord is a _______ | Drowned glacial trough |
| _______would have the largest capacity to naturally remove sewage pollutants. | Slightly clayey sand. |
| At a bend in a river, the main erosion is _____ | on the outside of the bed. |
| A name commonly used as a synonym for the Ice Age is _________ | Pleistocene Epoch |
| Running water is an important agent in many arid lands despite infrequent rainfalls. | True. |
| A ______is an erosional feature specifically produced by alpine glaciation. | U-shaped valley |
| Which one of the moraines listed below is NOT characteristic of continental glaciation? | Lateral moraine |
| Loose undisturbed particles assume a stable slope called the angle of repose. | True. |
| Steppes are the driest of the true desert lands. | False |
| A cirque represents an erosional feature formed in what was an important accumulation zone for snow and ice at the upstream head of a glacier. | True |
| Which one of the following factors does NOT influence stream velocity? | laminar flow |
| A_______ is the icicle-like speleothem that grows down from the roof of a cavern. | stalactite |
| Loose undisturbed particles assume a stable slope called the angle of repose. | true |
| ______generally constitutes the highest percentage of the annual sediment load moved by a stream. | Suspended load. |
| Which one of the following could not have significantly affected climatic variations and advances and retreats of ice sheets during the Pleistocene epoch? | movements of Earth's tectonic plates |
| Which one of the following concerning artesian wells is not true? | when the well penetrates the aquifer, the water rises to the bottom of the aquitard above the aquifer. |
| A ______is an intermittent stream channel in the dry land areas of the western United States. | wash |
| _______are erosional features produced by valley/alpine glaciers. | Cirques |
| Which one of the following is NOT true of glaciers? | exist only in the Northern Hemisphere. |
| The term drif_______ | means any sediment of glacial origin |
| the water table is | a boundary between saturated rock below and unsaturated rock above |
| When water is pumped from a well, a depression is often produced in the water table. Such a depression is an | cone of depression |
| Alluvium refers to stream deposits, mainly sand and gravel. | True |
| _______are characteristics of down cutting streams and youthful stage of a valley evolution. | Rapids and lots of whitewater |
| Desert pavement is the result of | deflation |
| Bajadas develop from coalescence of alluvian fans along fronts of mountain ranges in arid lands. | True |
| At a bend in a river, the main erosion is | on the outside of the bend. |
| Obsidian exhibits a_______texture. | glassy |
| Atoms of the same element, zinc for example, have the same number of ____________. | protons in the nucleus |
| Which one of the following is not true for minerals? | They can be a liquid, solid, or glass. |
| Which one of the following mineral groups exhibits a sheet-like silicate structure? | micas |
| Evaporites have a biochemical origin. | False |
| The micas, biotite and muscovite, both exhibit one direction of cleavage. | true |
| This dense, nonfoilated metamorphic rock is produced most often from sandstone. | quartzite |
| Igneous rock is formed | by crystallization of molten rock. |
| What element is the most abundant in the Earth's crust by weight? | oxygen |
| Which common mineral is composed entirely of silicon and oxygen? | quartz |
| The most abundant sedimentary rock is shale. | True |
| Which one of the following is an igneous rock? | Rhyolite |
| What mineral is the hardest known substance in nature? | Diamond |
| One magma can produce several different igneous rocks having different mineral compositions. | true |
| Select the coarse-grained rock which is composed mainly of quartz and potassium feldspar from the list below. | granite |
| which of these factors influence the type and rate of weathering? | all of these. |
| An atoms mass number is 13 and its atomic number is 6. How many neutrons are in its nucleus? | 7 |
| Which carbon mineral reacts readily with cool, dilute hydrochloric acid to produce visible bubbles of carbon dioxide gas? | calcite |
| Metamorphism can affect only sedimentary rocks. | False. |
| Which of the following best describes bedded gypsum and rock salt. | evaporites;chemical,sedimentary rocks. |
| A mineral can be composed entirely of one element. | True. |
| Atoms that have an electrical charge due to a gain or loss of electrons are called. | ions |
| Over 100 elements are currently known. | True. |
| Which of the rocks listed below is a popular building stone? | Granite |
| The ion at the center of a silicon-oxygen tetrahedron is surrounded by | 4 oxygen ions |
| Which of the following has the highest specific gravity? | gold |
| Rocks are aggregates of one or more minerals. | True |
| The primary agent of contact metamorphism is | heat |
| During metamorphism the material undergoing deformation remains a solid. | True. |
| Nearly 4,000 minerals have been named. | True. |
| Basalt is the fine-grained equivalent of gabbro. | True |
| Sedimentary rocks | all of these |
| Detrital sediments would predominate in all of the following environments except | Salt flat |
| Which of the following denotes the positively charged particles in an atoms nucleus? | PROTONS |
| The texture of an igneous rock | the rate of cooling of the melt: |
| Most limestone has a biochemical origin. | true |
| Which rock type is associated with high-energy environment(such as a very turbulent stream) | conglomerate |
| Which of the following is NOT one of the eight most common elements in Earth's crust? | carbon |
| __________is a strong, parallel alignment of different mineral bands in metamorphic rock. | FOLIATION |
| The micas, biotite, and muscovite both exhibit one direction of cleavage. | True |
| Which of the following describes light reflecting and transmission characteristics of a mineral? | luster |
| Chemical weathering would be most effective? | cold, wet climate |
| All silicate minerals contain which two elements? | silicon, oxygen |
| Isotopes of the same element have the same mass number. | False. |
| Quartz is quite resistant to weathering and is an important component of sands in riverbeds and on beaches. | True |
| The resistance of a mineral to abrasion is known as ________. | hardness |
| Mineral luster is broadly classified as either being metallic or opaque. | False |
| A cubic centimeter of quartz, olivine, and gold weigh 2.5, 3.0, and 19.8 grams respectively. This indicates that ________. | gold has a higher density and specific gravity than quartz and olivine |
| Diamond and quartz are both minerals composed of a single element. | False |
| his igneous texture is characterized by two distinctively different crystal sizes. | porphyritic |
| Most limestone has a biochemical origin. | True |
| Detrital sedimentary rocks are classified (named) primarily on the basis of ________. | particle size |
| All atoms of the same element have the same atomic number. | true |
| Which of the following is correct for isotopes of the same element? | the atoms have different numbers of neutrons and the same number of protons |
| Which mineral is easily soluble in water at room temperature conditions? | halite |
| Glassy igneous rocks form when magma cools too fast for mineral grains to grow. | TRUE |
| Which group of minerals are the most abundant in the Earth's crust? | Silicates |
| In the silicon-oxygen tetrahedron there are more silicon atoms than oxygen atoms. | False |
| Mineral deposits which have been identified and can be extracted profitably are called ________. | Reserves |
| Metamorphism is commonly associated with mountain building. | True |
| The common rock produced by the metamorphism of limestone is ________. | marble |
| Which of the following lists the rocks in the order of increasing grain size and increasing grade of metamorphism? | slate, phyllite, schist |
| Nonmetallic minerals like halite and gypsum have no industrial uses. | False |
| Which mineral is easily soluble in water at room temperature conditions? | halite |
| Chemical weathering would be most effective ________. | n a warm, humid climate |
| ntrusive rocks ________. | NONE OF THESE |
| Which pair of minerals is most common in detrital sedimentary rocks? | CLAY AND QUARTZ |
| Electrically neutral atoms have equal numbers of electrons and protons. | True |
| Which one of the following is NOT true about mechanical weathering? | does not affect metamorphic rocks |
| n the silicon-oxygen tetrahedron there are more silicon atoms than oxygen atoms. | false |
| The most abundant sedimentary rock is shale. | true |
| Which one of the following is an igneous rock? | rhyolite |
| Glassy igneous rocks form when magma cools too fast for mineral grains to grow. | True |
| The largest quantity of metamorphic rock is produced by regional metamorphism. | True |
| A cirque represents an erosional feature formed in what was an important accumulation zone for snow and ice at the upstream head of a glacier. | True |
| Which one of the following factors does NOT influence stream velocity? | Stream gradient, channel shape, and roughness of the channel. |
| Which one of the following is NOT true of glaciers? | exist only in the northern hemisphere. |
| he oldest rocks of the oceanic crust are found in deep ocean trenches far away from active, mid-ocean ridges. | True |
| During the geologic past, the magnetic field poles have generally been very close to Earth's rotational poles. | True |
| he Aleutian Islands occur at a ________ | convergent boundary on a volcanic arc above a northward-subducting Pacific plate |
| A transform plate boundary is characterized by ________. | a deep, vertical fault along which two plates slide past one another in opposite directions |
| The ________ is an example of an active, continent-continent collision? | northward movement of India into Eurasia |
| During various times in the geologic past, the polarity of Earth's magnetic field has been reversed. | True |
| Today, ________ is in about the same geographic position as during late Paleozoic time. | Antartica |
| Mount St. Helens and the other Cascade volcanoes are ________. | young, active stratovolcanoes built on a continental margin above a sinking slab of oceanic lithosphere |
| Pull-apart, rift zones are generally associated with a ________ plate boundary. | divergent |
| In the early part of the 20th century, ________ argued forcefully for continental drift. | Alfred Wegner |
| The volcanoes of Hawaii are localized above a deep mantle hot spot; they are not part of the East Pacific oceanic ridge | True |
| Where would you drill to recover samples of the oldest basalts of the oceanic crust, which are Jurassic in age? | oceanic side of the Aleutian trench |
| The continental drift hypothesis was rejected primarily because Alfred Wegener could not ________. | identify a mechanism capable of moving continents |
| ________ first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid-ocean ridge. | Vine and Matthews |
| Which of the following paleoclimatic evidence supports the idea of the late Paleozoic super continent in the Southern Hemisphere? | tillites (rocks formed by glaciers) in South Africa and South America |
| An extensive, late Paleozoic glaciation affected southern India, southern Africa and southeastern South America. | True |
| ________ was never proposed as evidence supporting the existence of Pangaea. | Islands of Precambrian rocks along the Mid-Atlantic Ridge |
| Iceland is a good example of an island arc, formed from an oceanic-oceanic plate collision. | False |
| The modern-day Red Sea is explained by plate tectonics theory because it is ________. | a rift zone that may eventually open into a major ocean if Arabia and Africa continue to separate |
| In general, rocks of the continental crust are less dense than rocks of the oceanic crust. | true |
| Linear, magnetic patterns associated with mid-ocean ridges are configured as ________. | normal and reversed magnetized strips roughly parallel to the ridge |
| Earth's radius and surface area are slowly increasing to accommodate the new oceanic crust being formed at mid-ocean ridges. | False |
| he rate of seafloor spreading is, on the average, about one meter per year. | False |
| Hawaii is the oldest island of the Hawaiian Island chain. | False |
| A very long-lived magma source located deep in the mantle is called a ________. | hot spot |
| Early results of the Deep Sea Drilling Project clearly justified the conclusion that ________. | the ocean basins are relatively young; most ocean basin rocks and sediments are Cretaceous or younger in age |
| Which one of the following most accurately describes the volcanoes of the Hawaiian Islands? | shield volcanoes fed by a long-lived hot spot below the Pacific lithospheric plate |
| Which of the following energy sources is thought to drive the lateral motions of Earth's lithospheric plates? | export of heat from deep in the mantle to the top of the asthenosphere |
| Cooler, older, oceanic lithosphere sink into the mantle at ________. | subduction zones along convergent plate boundaries |
| Seafloor spreading rates can be estimated if the geologic ages of the magnetic field reversals are independently known. | True |
| The Himalayan Mountains and Tibetan Plateau are still rising today as Eurasia slides beneath the Indian subcontinent. | False |
| Accretionary wedges develop along subduction zones where sediments and other rocks are scraped off a descending plate and piled against the leading edge of the overriding plate. | True |
| The lithosphere is defined as ________. | a rigid layer of crustal and mantle material |
| Continental crustis generally thicker than oceanic crust. | true |
| the elastic rebound theory for the origin of earthquakes was first proposed by ________ following the ________ earthquake. | Reid; 1906, San Francisco |
| The Sierra Nevada, CA, and Teton, WY ranges are examples of ________. | fault blocks uplifted by late Tertiary to Quaternary normal faulting |
| Which one of the following statements about the crust is NOT true? | oceanic crust is enriched in potassium, sodium, and silicon |
| The Mercalli Scale is a scale from ________. | I to XII that rates the structural damage due to an earthquake |
| In a reverse fault, the hanging wall block moves up relative to the footwall block. | True |
| A horst is ________. | an uplifted block bounded by two normal faults |
| Unconsolidated, water-saturated soils or sediments provide good foundation materials for buildings and other structures. | False |
| Which of the following combinations should favor folding rather than faulting? | high temperature and high confining pressure |
| Large circular downwarped structures are called ________. | basins |
| The asthenosphere is located ________. | the upper mantle |
| The ________ magnitude scale is a measure of the energy release | Richter |
| The ________ is (are) characterized by terrane accretion that has been active throughout most of Mesozoic and Cenozoic time. | western margin of North America |
| S waves can travel through solid and liquid media. | False |
| A graben is an upraised block bounded by two reverse faults. | False |
| On a typical seismogram, ________ will show the highest amplitudes. | surface waves |
| The Richter magnitude of an earthquake is determined from the ________. | |
| The ________ in California is the boundary between the North American and Pacific plates. | San Andreas strike-slip fault |
| The ________ earthquake was accompanied by extensive fire damage. | San Francisco, 1906 |
| Earthquakes result from the sudden release of elastic strain energy previously stored in rocks surrounding a zone of fault movement. | True |
| Which one of the following is true regarding tsunamis? | they occur in the open ocean, wavelengths are many miles or kilometers and wave heights are only a few feet |
| Brittle deformation would be favored over plastic deformation in which of the following conditions? | cooler temperatures |
| Which one of the following statements is correct? | |
| ________ is the maximum possible damage designation on the Mercalli scale. | XII |
| In a normal fault ________. | the hanging wall block above an inclined fault plane moves downward relative to the other block |
| The Richter earthquake magnitude scale is based on the total amount of energy released by the earthquake. | True |
| A graben is characterized by ________. | a hanging wall block that has moved down between two normal faults |
| ________ magma is the most abundant type of magma erupted at oceanic spreading centers. | Basaltic |
| Small amounts of water can lower partial melting temperatures in silicate rocks. | True |
| Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface? | pahoehoe |
| In general, cinder cones are much larger than shield volcanoes. | False |
| ________ destroyed the city of St. Pierre, Martinique in 1902. | A nueé ardente |
| Which statement about the May, 1980, eruption of Mount St. Helens is false? | during the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris |
| Kilauea and Mauna Loa are ________. | basaltic shield volcanoes |
| Vents that emit only heated, volcanic gases and water are called fumaroles. | True |
| The active Hawaiian volcanoes are situated directly above a major boundary between two of the Earth's largest tectonic plates | False |
| The largest igneous intrusive body is called a(n) ________. | BATHOLITH |
| Which of the following statements best describes the big Hawaiian volcanoes? | are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle |
| Which kind of volcanism is typical of mid-oceanic ridge systems? | submarine; basaltic lava flows |
| Most basaltic magmas are believed to form by partial melting of granite in the lower crust and upper mantle. | FALSE |
| Which of the following is associated with deep mantle hot spots? | the volcanoes of Hawaii and Quaternary activity in Yellowstone National Park |
| ________ are usually the most abundant gases emitted during basaltic volcanism. | Water and carbon dioxide |
| Most of the active volcanoes on Earth are located in a belt known as the ________. | Ring of FIRE |
| The 1943 eruption of Paricutin in Mexico was characterized by ________. | cinder cone building and basaltic lava |
| Magma tends to rise toward Earth's surface principally because | rocks become less dense when they melt |
| Paricutin is an example of a ________. | CINDER CONE |
| A ________ is the largest, discordant body of intrusive, igneous rock. | BATHOLITH |
| The 1991 Pinatubo eruption in the Philippines caused brilliantly colored sunrises and sunsets to be seen for the next few years. What caused this phenomenon? | sulfur dioxide and other erupted gases formed aerosols in the stratosphere |
| Which region has the greatest concentration of currently active volcanoes? | the circum-Pacific area |
| Basalt is the most common magma erupted along oceanic rift systems. | TRUE |
| A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows. | SHIELD |
| Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble? | aa |
| The ________ ocean basin is rimmed by the most subduction zones. | PACIFIC |
| Spreading center volcanism most generally produces rocks which are ________. | basaltic in composition |
| Kilauea is an example of a ________. | SHIELD VOLCANO |
| Magma generation at depth almost always involves partial melting, not complete melting of the source rock. | True |
| Most basaltic magmas are believed to form by partial melting of granite in the lower crust and upper mantle. | False |
| Ash and Lapilli are different sized pyroclastic particles. | TRUE |
| ______is a major dissolved volatile constituent in both magmas and volcanic gases? | water |
| _____tend to increase the explosive potential of magma body beneath a volcano. | High viscosity and dissolved gas |
| The Icelandic volcanoes are related to plate tectonics because | They lie on a spreading center where two plates are moving apart. |
| Vents that emit only heated, volcanic gases and water are called fumaroles. | True |
| Which kind of volcanism is typical of mid-oceanic ridge systems? | submarine;basaltic lava flows |
| In 1980,______ was the first Cascade Range Volcano to erupt since Mt. Lassen in 1915-16 | Mt. ST. HELENS |
| The eruptions of the Hawaiin volcanoes may be described as explosive in comparison to the 1980 Mount St. Helens eruption. | False |
| Which statement about the May, 1980, eruption of MOunt St. Helens is false? | During the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris. |
| Which of the following statements best describes the big Hawaiin volcanoes? | are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle |
| Small amounts of water can lower partial melting temperatures in silicate rocks. | True |
| ________magma is the most abundant type of magma erupted at oceanic spreading centers. | Basaltic |
| The 1943 Eruption of Paricutin Mexico was characterized by | Cinder cone building and basaltic lava |
| Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be covered by flood basalts. | True |
| A_______is a near surface, intrusive igneous rock body that results from local inflation of a horizontal sill. | Laccolith |
| The era of "ancient life" is the ________ era. | Paleozoic |
| Which of the following is an essential characteristic of an index fossil? | the organism only lived for a short period of geologic time |
| Which of the following geologic observations would not bear directly on working out the sequence of geologic events in an area? | the feldspar and quartz contents of a granite |
| The geologic time scale was devised before numerical dating using radioactivity was invented. | the feldspar and quartz contents of a granite |
| The geologic time scale was devised before numerical dating using radioactivity was invented. | True |
| Consider the names of the eras in the geologic time scale. What is meant by "zoic"? | life; living things |
| What is the age of the Earth accepted by most scientists today? | 4.5 billion years |
| The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today? | between one-fourth and one-eighth |
| An unconformity is a buried ________. | surface of erosion separating younger strata above from older strata below |
| When a radioactive isotope decays by electron capture, the electron ________. | combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent |
| What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? | law of superposition |
| When a beta particle is emitted, the mass number of the isotope remains unchanged. | true |
| After three half-lives, one-ninth of an original, radioactive, parent isotope remains and eight-ninths has decayed into the daughter isotope. | False |
| Who made the first clear statement of the law of superposition? When? | Nicolaus Steno, 17th century |
| Radiometric dating means placing events in their proper sequence. | False |
| The ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| Visualize five, horizontal, sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true? | beds l and 3 are older than bed 4 |
| The ________ is the idea or concept that ancient life forms succeeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata? | principle of faunal succession |
| Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest? | eon, era, period, epoch |
| Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically? | the granite is older if the sandstone contains pebbles of the granite |
| he era known as the "age of mammals" is the ________. | Cenozoic |
| In the late 1700s James Hutton published his important work titled ________. | Theory of the Earth |
| An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity. | TRUE |
| The Paleozoic is the era of "ancient life." | TRUE |
| Correlation of rock units between continents or widely separated areas is accomplished by using physical features such as color, texture, and thickness of units. | TRUE |
| The term Mesozoic refers to life forms intermediate in complexity between early and much later, more modern-looking life forms. | TRUE |
| Assume that you have just examined several flat-lying sedimentary layers. After much study you determine that there is a considerable span of time for which no sedimentary rock layer exists at this site. You have just discovered a(n) ________ | disconformity |
| The subdivision of the geologic time scale that represents the shortest time span is called a(n) ________. | epoch |
| Which of the following describes radioactive decay by beta particle emission? | the atomic number of the daughter isotope is one more than the parent; the mass numbers are the same |
| ________ is an erosional contact between tilted, older strata below and horizontal, younger strata above. | An angular unconformity |
| Melting and calving are two forms of ablation. | TRUE |
| Which one of the following applies to a valley glacier that lengthens (extends its terminus downslope) over a period of many years? | accumulation exceeds wastage |
| Which of the following terms is used to describe the way materials move during a mass wasting event? | all of these |
| Rejuvenation of a stream may be due to ________. | uplift of land |
| ________ is one of the two, major flow mechanism in a glacier. | basal slip |
| Ice Age glaciers had many indirect effects. Which one of the following was NOT such an effect? | extinction of some organizims |
| Blowouts are broad, shallow depressions excavated by deflation. | true |
| The water table is ________. | a boundary between saturated rock below and unsaturated rock above |
| If you were to examine the longitudinal profile of a typical river, you would probably find that the gradient is ________. | steepest near the head |
| ________ is an irregular, usually thin till layer laid down by a retreating glacier. | ground moraine |
| The temperature below which magnetic material can retain a permanent magnetization is called the ______ | Curie Point |
| A fiord is a ________. | drowned glacial trough |
| What mature, desert landscape feature consists of coalesced alluvial fans? | bajada |
| The term karst topography was first used in ________. | the Republic of Slovenia, a province of the former Yugoslavia |
| The formation of stalactites and stalagmites occurs in the zone of saturation. | false |
| At the head of a delta, the major channel splits into smaller channels that follow different paths to the sea. These smaller channels are known as ________. | distributaries |
| Which one of the following statements is true? | despite infrequent rainfalls, erosional and depositional features of running water are important in desert landscapes |
| Running water is an important erosional agent in many arid lands despite infrequent rainfalls. | True |
| A ________ stream pattern is developed only on growing mountains like volcanoes or where the land surface is tectonically doming upward. | radial |
| The single most important erosional agent is ________. | running water |
| Crevasses are short, narrow cracks in the plastic flow zone of a glacier that alternately open and close as the ice flows along. | false |
| Point bars are depositional features located along the outer portions of meander bends. | false |
| Bajadas develop from coalescence of alluvial fans along fronts of mountain ranges in arid lands. | true |
| For a well to be characterized as being artesian, water must flow freely at the surface. | false |
| Which one of the moraines listed below is NOT characteristic of continental glaciation? | lateral moraine |
| ________ is an erosional contact between tilted, older strata below and horizontal, younger strata above. | An angular unconformity |
| Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time? | one millionth |
| The ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| An unconformity is a buried ________. | surface of erosion separating younger strata above from older strata below |
| ________ is an erosional contact between tilted, older strata below and horizontal, younger strata above. | An angular unconformity |
| An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity. | True |
| Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest? | eon, era, period, epoch |
| What is the age of the Earth accepted by most scientists today? | 4.5 billion years |
| In the late 1700s James Hutton published his important work titled ________. | Theory of the Earth |
| The term Paleozoic describes the era of ancient life forms. | True |
| The era of "ancient life" is the ________ era. | Paleozoic |
| The Paleozoic is the era of "ancient life." | true |
| What of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas? | correlation |
| A worm would stand a poor chance of being fossilized because ________. | worms have no hard parts |
| When a beta particle is emitted, the mass number of the isotope remains unchanged. | True |
| Phanerozoic, marine, sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages. | True |
| The subdivision of the geologic time scale that represents the shortest time span is called a(n) ________. | epoch |
| After three half-lives, one-ninth of an original, radioactive, parent isotope remains and eight-ninths has decayed into the daughter isotope. | False |
| Phanerozoic, marine, sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages. | True |
| The term Mesozoic refers to life forms intermediate in complexity between early and much later, more modern-looking life forms. | True |
| When a radioactive isotope decays by electron capture, the electron ________. | combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent |
| By applying the law of superposition ________ dates can be determined. | relative |
| Who is credited with formulating the doctrine of uniformitarianism? | Hutton |
| Which of the following best characterizes an angular unconformity? | tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity |
| The geologic time scale was devised before numerical dating using radioactivity was invented. | true |
| The ________ is the idea or concept that ancient life forms succeeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata? | principle of faunal succession |
| Which of the following describes radioactive decay by beta particle emission? | the atomic number of the daughter isotope is one more than the parent; the mass numbers are the same |
| What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? | law of superposition |
| The era known as the "age of mammals" is the ________. | Cenozoic |
| Who made the first clear statement of the law of superposition? When? | Nicolaus Steno, 17th century |
| Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time? | one millionth |
| The ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| An unconformity is a buried ________. | surface of erosion separating younger strata above from older strata below |
| ________ is an erosional contact between tilted, older strata below and horizontal, younger strata above. | An angular unconformity |
| Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time? | one millionth |
| The ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| An unconformity is a buried ________. | surface of erosion separating younger strata above from older strata below |
| ________ is an erosional contact between tilted, older strata below and horizontal, younger strata above | An angular unconformity |
| An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity. | True |
| What of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas? | correlation |
| A worm would stand a poor chance of being fossilized because ________. | worms have no hard parts |
| Phanerozoic, marine, sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages. | True |
| When a beta particle is emitted, the mass number of the isotope remains unchanged. | True |
| After three half-lives, one-ninth of an original, radioactive, parent isotope remains and eight-ninths has decayed into the daughter isotope. | False |
| The term Mesozoic refers to life forms intermediate in complexity between early and much later, more modern-looking life forms. | TRUE |
| When a radioactive isotope decays by electron capture, the electron ________. | combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent |
| By applying the law of superposition ________ dates can be determined. | relative |
| Who is credited with formulating the doctrine of uniformitarianism? | Hutton |
| Which of the following best characterizes an angular unconformity? | tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity |
| What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? | law of superposition |
| Which of the following best characterizes an angular unconformity? | tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity |
| Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time? | one millionth |
| he ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| An unconformity is a buried ________ | surface of erosion separating younger strata above from older strata below |
| Which of the following describes radioactive decay by beta particle emission? | the atomic number of the daughter isotope is one more than the parent; the mass numbers are the same |
| What of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas? | correlation |
| Which of the following best characterizes an angular unconformity? | tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity |
| The temperature below which magnetic material can retain a permanent magnetization is called the ______ | Curie point |
| The former, late Paleozoic super continent is known as ________. | PANGAEA |
| The rate of seafloor spreading is, on the average, about one meter per year. | FALSE |
| The ________ is an example of an active, continent-continent collision? | northward movement of India into Eurasia |
| Seafloor spreading rates can be estimated if the geologic ages of the magnetic field reversals are independently known. | TRUE |
| Which of the following paleoclimatic evidence supports the idea of the late Paleozoic super continent in the Southern Hemisphere? | tillites (rocks formed by glaciers) in South Africa and South America |
| Which of the following statements apply to the asthenosphere, but not the lithosphere? | zone in the upper mantle that deforms by plastic flowage |
| As the South Atlantic basin widens by seafloor spreading, Africa and South America are moving closer together. | FALSE |
| Earth's radius and surface area are slowly increasing to accommodate the new oceanic crust being formed at mid-ocean ridges. | FALSE |
| During various times in the geologic past, the polarity of Earth's magnetic field has been reversed. | TRUE |
| In general, rocks of the continental crust are less dense than rocks of the oceanic crust. | TRUE |
| A typical rate of seafloor spreading in the Atlantic Ocean is ________. | 2 centimeters per year |
| Where would you drill to recover samples of the oldest basalts of the oceanic crust, which are Jurassic in age? | oceanic side of the Aleutian trench |
| The Aleutian Islands occur at a ______ | convergent boundary on a volcanic arc above a northward-subducting Pacific plate |
| The volcanoes and deep valleys of east Africa are related to a ________ | continental rift along which parts of the African continent are beginning to slowly separate |
| Today, ________ is in about the same geographic position as during late Paleozoic time. | Antarctica |
| The oldest rocks of the oceanic crust are found in deep ocean trenches far away from active, mid-ocean ridges. | TRUE |
| A transform plate boundary is characterized by ________. | a deep, vertical fault along which two plates slide past one another in opposite directions |
| Cooler, older, oceanic lithosphere sink into the mantle at ________. | subduction zones along convergent plate boundaries |
| An extensive, late Paleozoic glaciation affected southern India, southern Africa and southeastern South America. | TRUE |
| During the geologic past, the magnetic field poles have generally been very close to Earth's rotational poles. | TRUE |
| The modern-day Red Sea is explained by plate tectonics theory because it is ________. | a rift zone that may eventually open into a major ocean if Arabia and Africa continue to separate |
| ________ was never proposed as evidence supporting the existence of Pangaea. | Islands of Precambrian rocks along the Mid-Atlantic Ridge |
| ________ first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid-ocean ridge. | Vine and Matthews |
| Which one of the following is an important fundamental assumption underlying the plate tectonic theory? | Earth's diameter has been essentially constant over time |
| ________ most effectively outline the edges of the lithospheric plates. | Lines of earthquake epicenters |
| ________ was an ancient reptile that lived in South America and Africa during the late Paleozoic. | Mesosaurus |
| The Black Hills of South Dakota are a good example of a(n) ________. | DOME |
| A graben is an upraised block bounded by two reverse faults. | FALSE |
| The Richter earthquake magnitude scale is based on the total amount of energy released by the earthquake. | TRUE |
| On a typical seismogram, ________ will show the highest amplitudes. | surface waves |
| A horst is ________. | an uplifted block bounded by two normal faults |
| Basin and range topography, like that in the western and southwestern United States, indicates that compressive folding is active today or was active very recently, geologically speaking. | FALSE |
| Earthquakes result from the sudden release of elastic strain energy previously stored in rocks surrounding a zone of fault movement. | TRUE |
| The average composition of the continental crust most closely approximates that of ________. | granite |
| he ________ are a geologically old mountain range folded and deformed during the Paleozoic. | Appalachians in the eastern United States |
| Continental crustis generally thicker than oceanic crust. | TRUE |
| Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5? | 30 TIMES |
| The ________ magnitude scale is a measure of the energy release | Richter |
| The mechanism by which rocks store and eventually release energy in the form of an earthquake is termed ________. | elastic rebound |
| The record of an earthquake obtained from a seismic instrument is a(n) ________. | seismogram |
| A graben is characterized by ________. | a hanging wall block that has moved down between two normal faults |
| In a ________ fault, the hanging wall block move up with respect to the footwall block | REVERSE |
| Which one of the following statements is correct? | S waves travel through solids and P waves travel through liquids |
| The elastic rebound theory for the origin of earthquakes was first proposed by ________ following the ________ earthquake. | Reid; 1906, San Francisco |
| The Himalayan Mountains and Tibetan Plateau are still rising today as Eurasia slides beneath the Indian subcontinent. | False |
| The asthenosphere is located ________. | in the upper mantle |
| The lithosphere is defined as ________. | a rigid layer of crustal and mantle material |
| Most of our knowledge about Earth's interior comes from ________. | seismic waves |
| S waves can travel through solid and liquid media. | False |
| Unconsolidated, water-saturated soils or sediments provide good foundation materials for buildings and other structures. | FALSE |
| In a reverse fault, the hanging wall block moves up relative to the footwall block. | TRUE |
| The ________ is (are) characterized by terrane accretion that has been active throughout most of Mesozoic and Cenozoic time. | western margin of North America |
| The Mercalli Scale is a scale from ________. | I to XII that rates the structural damage due to an earthquake |
| Accretionary wedges develop along subduction zones where sediments and other rocks are scraped off a descending plate and piled against the leading edge of the overriding plate. | T R U E |
| Which of the following combinations should favor folding rather than faulting? | high temperature and high confining pressure |
| The ________ earthquake was accompanied by extensive fire damage. | San Francisco, 1906 |
| Which one of the following is true regarding tsunamis? | they occur in the open ocean, wavelengths are many miles or kilometers and wave heights are only a few feet |
| Which of the following combinations should favor folding rather than faulting? | high temperature and high confining pressure |
| The mantle is composed mainly of metallic iron with small amounts of magnesium silicate minerals. | FALSE |
| The Richter magnitude of an earthquake is determined from the ________. | amplitude of the largest seismic wave recorded |
| The Himalayan Mountains and Tibetan Plateau are still rising today as Eurasia slides beneath the Indian subcontinent. | FALSE |
| S waves can travel through solid and liquid media. | FALSE |
| In a reverse fault, the hanging wall block moves up relative to the footwall block. | TRUE |
| A graben is an upraised block bounded by two reverse faults. | FALSE |
| The mechanism by which rocks store and eventually release energy in the form of an earthquake is termed ________. | ELASTIC REBOUND |
| Most of our knowledge about Earth's interior comes from ________. | seismic waves |
| In a ________ fault, the hanging wall block move up with respect to the footwall block. | reverse |
| The Sierra Nevada, CA, and Teton, WY ranges are examples of ________. | fault blocks uplifted by late Tertiary to Quaternary normal faulting |
| In a normal fault ________. | the hanging wall block above an inclined fault plane moves downward relative to the other block |
| The ________ are a geologically old mountain range folded and deformed during the Paleozoic. | Appalachians in the eastern United States |
| Large circular downwarped structures are called ________. | BASINS |
| On a typical seismogram, ________ will show the highest amplitudes. | surface waves |
| Basin and range topography, like that in the western and southwestern United States, indicates that compressive folding is active today or was active very recently, geologically speaking. | FALSE |
| The average composition of the continental crust most closely approximates that of ________. | GRANITE |
| Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5? | 30 TIMES |
| A horst is ________. | an uplifted block bounded by two normal faults |
| The lithosphere is defined as ________. | a rigid layer of crustal and mantle material |
| Which one of the following statements is correct? | S waves travel through solids and P waves travel through liquids. |
| Which one of the following statements about the crust is NOT true? | oceanic crust is enriched in potassium, sodium, and silicon |
| Which statement about the May, 1980, eruption of Mount St. Helens is false? | during the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris |
| Vents that emit only heated, volcanic gases and water are called fumaroles. | TRUE |
| ________ are usually the most abundant gases emitted during basaltic volcanism. | water and carbon dioxide |
| A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows. | shield |
| Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface? | pahoehoe |
| Which of the following is associated with deep mantle hot spots? | the volcanoes of Hawaii and Quaternary activity in Yellowstone National Park |
| The active Hawaiian volcanoes are situated directly above a major boundary between two of the Earth's largest tectonic plates. | FALSE |
| Spreading center volcanism most generally produces rocks which are ________. | basaltic in composition |
| Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble? | aa |
| Which of the following statements best describes the big Hawaiian volcanoes? | are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle |
| The 1943 eruption of Paricutin in Mexico was characterized by ________. | cinder cone building and basaltic lava |
| Most basaltic magmas are believed to form by partial melting of granite in the lower crust and upper mantle. | FALSE |
| Magma tends to rise toward Earth's surface principally because | rocks become less dense when they melt |
| In 1980, ________ was the first Cascade Range volcano to erupt since Mt. Lassen in 1915-16. | Mt. St. Helens |
| The recent (geologically) volcanic activity in Yellowstone National Park is ________. | related to intraplate, hot spot volcanism |
| The eruptions of the Hawaiian volcanoes may be described as explosive in comparison to the 1980 Mount St. Helens eruption. | FALSE |
| The 1991 Pinatubo eruption in the Philippines caused brilliantly colored sunrises and sunsets to be seen for the next few years. What caused this phenomenon? | sulfur dioxide and other erupted gases formed aerosols in the stratosphere |
| ________ destroyed the city of St. Pierre, Martinique in 1902. | A nueé ardente |
| Kilauea is an example of a ________. | shield volcano |
| In general, cinder cones are much larger than shield volcanoes. | False |
| A ________ is a near surface, intrusive, igneous rock body that results from local inflation of a horizontal sill. | laccolith |
| ________ magma is the most abundant type of magma erupted at oceanic spreading centers. | BASALTIC |
| Which kind of volcanism is typical of mid-oceanic ridge systems? | submarine; basaltic lava flows |
| The Icelandic volcanoes are related to plate tectonics because ________. | they lie on a spreading center where two plates are moving apart |
| Kilauea and Mauna Loa are ________. | basaltic shield volcanoes |
| The ________ ocean basin is rimmed by the most subduction zones. | PACIFIC |
| What volcanic events formed Crater Lake, OR? When did they take place? | caldera collapse followed major ash and pyroclastic-flow eruptions; 6000 years ago |
| Small amounts of water can lower partial melting temperatures in silicate rocks. | TRUE |
| The largest igneous intrusive body is called a(n) ________. | batholith |
| _______ are usually the most abundant gases emitted during basaltic volcanism. | water and carbon dioxide |
| A ________ is the largest, discordant body of intrusive, igneous rock. | batholith |
| Which statement about the May, 1980, eruption of Mount St. Helens is false? | during the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris |
| Basalt is the most common magma erupted along oceanic rift systems. | TRUE |
| Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble? | aa |
| Which kind of volcanism is typical of mid-oceanic ridge systems? | submarine;basaltic lava flows |
| Which of the following is associated with deep mantle hot spots? | the volcanoes of Hawaii and Quaternary activity in Yellowstone National Park |
| The 1943 eruption of Paricutin in Mexico was characterized by ________. | cinder cone building and basaltic lava |
| Paricutin is an example of a ________. | cinder cone |
| Vents that emit only heated, volcanic gases and water are called fumaroles. | True |
| Magma generation at depth almost always involves partial melting, not complete melting of the source rock. | true |
| ________ destroyed the city of St. Pierre, Martinique in 1902. | A nueé ardente |
| Kilauea is an example of a ________. | shield volcano |
| The ________ ocean basin is rimmed by the most subduction zones. | pacific |
| ________ magma is the most abundant type of magma erupted at oceanic spreading centers. | Basaltic |
| In 1980, ________ was the first Cascade Range volcano to erupt since Mt. Lassen in 1915-16. | Mt. St. Helens |
| The eruptions of the Hawaiian volcanoes may be described as explosive in comparison to the 1980 Mount St. Helens eruption. | False |
| Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be covered by flood basalts. | TRUE |
| Which region has the greatest concentration of currently active volcanoes? | the circum-Pacific area |
| ________ tend to increase the explosive potential of a magma body beneath a volcano. | High viscosity and dissolved gas. |
| Kilauea and Mauna Loa are ________. | basaltic shield volcanoes |
| Which of the following statements best describes the big Hawaiian volcanoes? | are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle |
| ________ is a major dissolved volatile constituent in both magmas and volcanic gases? | water |
| A ________ is a near surface, intrusive, igneous rock body that results from local inflation of a horizontal sill. | LACCOLITH |
| Spreading center volcanism most generally produces rocks which are ________. | basaltic in composition |
| Small amounts of water can lower partial melting temperatures in silicate rocks. | true |
| Ash and lapilli are different sized pyroclastic particles. | True |
| The recent (geologically) volcanic activity in Yellowstone National Park is ________. | related to intraplate, hot spot volcanism |
| The era of "ancient life" is the ________ era. | Paleozoic |
| Which of the following is an essential characteristic of an index fossil? | the organism only lived for a short period of geologic time |
| Catastrophism ________. | was a philosophy that was first expounded by the early Greeks |
| Which of the following geologic observations would not bear directly on working out the sequence of geologic events in an area? | the feldspar and quartz contents of a granite |
| The geologic time scale was devised before numerical dating using radioactivity was invented. | True |
| Consider the names of the eras in the geologic time scale. What is meant by "zoic"? | life;living things |
| What is the age of the Earth accepted by most scientists today? | 4.5 billion years |
| The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today? | between one-fourth and one-eighth |
| When a radioactive isotope decays by electron capture, the electron ________. | combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent |
| What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? | law of superposition |
| When a beta particle is emitted, the mass number of the isotope remains unchanged. | TRUE |
| After three half-lives, one-ninth of an original, radioactive, parent isotope remains and eight-ninths has decayed into the daughter isotope. | False |
| Who made the first clear statement of the law of superposition? When? | Nicolaus Steno, 17th century |
| Radiometric dating means placing events in their proper sequence. | FALSE |
| The ratio of parent to daughter isotopes in a radioactive decay process is 0.40 How many half-lives have elapsed since the material was 100% parent atoms? | between l and 2 |
| Visualize five, horizontal, sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true? | beds l and 3 are older than bed 4 |
| The ________ is the idea or concept that ancient life forms succeeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata? | principle of faunal succession |
| Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest? | eon, era, period, epoch |
| Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically? | the granite is older if the sandstone contains pebbles of the granite |
| The era known as the "age of mammals" is the ________. | Cenozoic |
| n the late 1700s James Hutton published his important work titled ________. | Theory of the Earth |
| An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity. | TRUE |
| The Paleozoic is the era of "ancient life." | TRUE |
| The term Mesozoic refers to life forms intermediate in complexity between early and much later, more modern-looking life forms. | TRUE |
| Correlation of rock units between continents or widely separated areas is accomplished by using physical features such as color, texture, and thickness of units. | FALSE |
| Assume that you have just examined several flat-lying sedimentary layers. After much study you determine that there is a considerable span of time for which no sedimentary rock layer exists at this site. You have just discovered a(n) ________. | disconformity |
| The subdivision of the geologic time scale that represents the shortest time span is called a(n) ________. | epoch |
| Which of the following describes radioactive decay by beta particle emission? | the atomic number of the daughter isotope is one more than the parent; the mass numbers are the same |
| Which of the following geologic observations would not bear directly on working out the sequence of geologic events in an area? | the feldspar and quartz contents of a granite |
| Visualize five, horizontal, sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true? | beds l and 3 are older than bed 4 |
| Who made the first clear statement of the law of superposition? When? | Nicolaus Steno, 17th century |
| Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time? | one millionth |
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