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ch 11 sec 1
how rock deforms
| Question | Answer |
|---|---|
| bending, tilting, and breaking of the Earth's crust | deformation |
| balancing of the forces pressing up and down on the Earth's crust | isostasy |
| the amount of force per unit area that is placed on a given material | stress |
| any change in rock from stress | strain |
| a form of ductile strain in which rock layers bend, usually as a result of compression | fold |
| break in rock along which rocks on either side of the break move | fault |
| As mountains become smaller and lighter due to erosion the area may rise by isostatic adjustment. this process is called _____ | uplift |
| rising of rock layers | uplift |
| sinking of rock layers (when material from rivers flowing into oceans deposits onto ocean floor, this occurs) | subsidence |
| stress at a divergent plate boundary | tension |
| stress at a convergent plate boundary | compression |
| upward arching rock layer | anticline |
| downward arching rock layer | syncline |
| hanging wall moves down relative to footwall | normal fault |
| hanging wall moves up relative to footwall | reverse fault |
| what is deformation? | bending, tilting or breaking of the Earth's crust |
| When the weight of part of the Earth's crust changes what sometimes occurs? | deformation |
| What is the asthenosphere? | plastic part of the mantle |
| When parts of the lithosphere thicken and become heavier, they what? | sink deeper into the asthenosphere |
| If parts of the lithosphere thin and become lighter, what happens | the lithosphere rises higher in the asthenosphere |
| A condition of gravitational and buoyant equilibrium between Earth's lithosphere and asthenosphere is called what? | isostasy |
| How often do isostatic adjustments occur in mountain regions? | constantly |
| What is the effect of erosion on mountains? | reduce height and weight of mountain range |
| describe the process called uplift? | as mountains become smaller and lighter, the area may rise by isostatic adjustment (this is called uplift) |
| Describe the process of subsidence | the added weight by deposited materials carried by a river to a nearby ocean floor caused ocean floor to sink by isostatic adjustment |
| When glaciers and ice sheets melt, what happens to the land they covered? | the land that was covered by ice slowly rises (by isostatic adjustment) |
| when glaciers and ice sheets melt, what happens to the ocean floor | as the glaciers melt, water returns to ocean and ocean floor gets heavier so ocean floor sinks by isostatic adjustment |
| What changes occur in rock in the Earth's crust as the lithosphere moves? | it is squeezed, stretched and twisted |
| What is stress? | the amount of force exerted on each unit of area |
| The type of stress that squeezes and shortens a body is called? | compression |
| In addition to reducing the amount of space that rock occupies, compression does what? | pushes rocks higher up or deeper down into the crust |
| Where is one place that compression occurs | where tectonic plates collide |
| stress that stretches and pulls a body of rock apart is called | tension |
| when tension pulls rocks apart the rocks become what? | thinner |
| Where is one place that tension occurs (what boundary) | near divergent boundaries, where tectonic plates pull apart |
| type of stress that distorts a body of rock by pushing parts of the body in opposite directions | shear stress |
| what happens to sheared rocks when they slide past each other? | they bend, twist or break |
| Where is shear stress common? | common at transform plate boundaries |
| What is strain? | any change in shape or volume of rock caused by stress |
| The amount of stress rock can withstand without changing shape permanently is ________. | limited |
| Materials that break as a result of stress are said to be _________ | brittle |
| Materials that bend or deform without breaking as a result of stress are referred to as _______. | ductile |
| what affects whether rock is brittle or ductile? | composition of rock (what types of rocks) |
| What other two factors also affect how rock will deform? | temperature and pressure |
| name the three things that affect how rocks deform? | composition, temperature, and pressure |
| In what way will rock deform at lower temperature and pressure and at higher temperature and pressure? | lower temp and pressure - deform in brittle way and higher temp and pressure - deform in ductile way |
| what three factors determine the type of strain that stress will cause to rocks? | 1. amount of stress 2. type of stress 3. rate at which stress is applied |
| What is a fold? | a bend in rock layers that results from stress |
| Rock folds are most easily observed where? | where flat layers of rock where compressed inward |
| True or False In folds, sometimes cracks appear, but most commonly the rock layers remain intact. | true (because they are folding not breaking, duhhhhhh) |
| What are the two types of stress that can cause a fold? | compression or shear stress |
| What are the sloping sides of folds called | limb |
| What is the area in a fold called where limbs meet at the bend in the rock layer | hinge |
| What is the term for a plane that can slice a symmetrical fold | axial plane |
| If a fold appears to be lying on its side, the fold is said to be _______________ | overturned |
| Why is each fold unique? | because the combination of stresses and conditions that cause the fold was unique |
| To categorize a fold, what do scientists study? | relative ages of the rocks in the fold |
| a fold in which both limbs are horizontal or almost horizontal | monocline |
| a large, narrow strip of elevated land, can occur near mountains | ridge |
| a fold in which the youngest layer is in the center, bowl shaped | syncline |
| a fold in which the oldest layer is in the center, arch shaped | anticline |
| How do monoclines form? | when one part of Earth's crust moves up or down relative to another part |
| Sometimes, a large anticline forms a ________. | ridge |
| What type of fold may cause a valley | a large syncline |
| what two types of folds formed the ridges and valleys of the Appalachian Mountains? | Anticline and Syncline folds |
| Stresses on rock close to Earth's surface, where temperatures and pressures are low, may cause the rock to | break |
| the surface along which the motion occurs in a fault is called | fault plane |
| in a nonvertical fault the rock below the fault plane is called | footwall |
| a break along which one block slides relative to another is called | fault |
| a break around which there is no movement of the surrounding rock is called | fracture |
| In a nonvertical fault the rock above the rock plane is called the | hanging wall |
| What is a normal fault and where does it usually form? | a fault where the hanging wall moves downward relative to the footwall. (forms at divergent boundaries) |
| What kind of landforms can normal faults form? | steep, steplike landforms |
| Give an example of a place with a steep, step-like landform formed by normal faults | Great Rift Valley of East Africa |
| How does a reverse fault form? | when compression causes the hanging wall to move upward relative to the footwall |
| What is a thrust fault? | special type of reverse fault in which the fault plane is at a low angle or nearly horizontal |
| Where are reverse faults and thrust faults common? | in mountain ranges such as the Rockies and the Alps |
| What does the strike of a fault describe? | the length of the fault |
| What is a strike-slip fault? | a fault in which the rock on either side of the fault plane slides horizontally |
| What is one example of a large fault system? | San Andreas fault in California |
Created by:
kellyaem