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The mantle
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Plate Tectonics.
Plate Tectonics PMEPP_TM_1118_Aut18
| Term | Definition |
|---|---|
| The crust | Outermost layer of the Earth |
| The mantle | Thicket layer of the Earth. Upper mantle = semi-molten state. Lower mantel = contains molten magma, capable of flow. |
| The outer core | Liquid state, mainly made up of iron. |
| The inner core | Hottest part of the Earth |
| Continental crust | Lies under the continents, thick and is also referred to as sial. |
| Oceanic crust | Lies under oceans. Thinner than continental crust. Made up of heavy rock. |
| Sea-floor spreading | 1960's. Harry Hess. New rock is formed where plates split apart. Mid-Atlantic Ridge. |
| Continental drift | Alfred Weagner. Continents were once together then broke up and drifted to their position they are in today. Pangaea. |
| Plates | Large sections of the earths crust that move due to convection currents in the mantle. |
| Divergent (constructive) plate boundaries | Two plates pull apart. Process: sea-floor spreading. Landforms: rift valleys, mid ocean ridges, volcanic islands. Example: Mid Atlantic Ridge, Iceland. |
| Convergent (destructive) plate boundaries | Two plates collide (rock is changed or destroyed) Oceanic-Oceanic Oceanic- Continental Continental- Continental |
| Oceanic-Oceanic | Process: subduction. Landforms: ocean trench, island arcs, earthquakes Example: Japan |
| Oceanic - Continental | Process: subduction Landforms: fold mountains, volcanos, ocean trenches Example: Andes and Rocky mountains |
| Continental- Continental | Process: subduction - crust fractures and buckles upwards. Landforms: fold mountains Example: Himalayas and the Alps. |
| Transform (Passive) plate boundaries | Two plates slide past each other. Rock is neither created nor destroyed. Process: seismic activity Landforms: fault lines, earthquakes Examples: San Andreas Fault |
| Types of folds | 1. Simple fold 2. Asymmetric fold 3.Overfold 4.Overthrust fold |
| Orogeny | Mountain building process caused by plate movement. |
| Caledonian Orogeny | When: 400 MYA Example: Wicklow Mountains, Ireland. American and Eurasian Plate collided. Reduced in height due to weathering and erosion. |
| Amorican Orogeny | When: 250 MYA Examples: Munster Ridge Valley African and Eurasian plate collided. |
| Alpine Orogeny | When 30 MYA Examples: Alps, Himalayas and Rocky Mountains Only folding period that did not affect Ireland. African and Indian plate collided. Youngest and highest mountain ranges. |
| Faulting | A moving fracture or break in the earths surface. Occurs at a place of weakness. 1. Normal fault - Clew Bay, Mayo. 2. Reverse fault - Pollatomish, Mayo. 3. Tear Fault - San Andres Fault, California. |
| Doming | Found in sedimentary rock. Earths surface bulges up creating a dome/ Example: Slieve Bloom Mountains, Laois and Offaly. |
| Earthquake | Shaking or vibrating of the Earth's crust. Occurs when pressure is suddenly released sending shock waves out from the focus deep in the earths crust. Directly above the epicenter. |
| Pacific Ring of Fire | Where the worlds most active volcanoes and earthquakes occur around the Pacific Ocean. |
| Seismographs | Machines used to measure the magnitude or strength of an earthquake P and S waves. Surface waves |
| Richter Scale | Measures the ground movement caused by and earthquake. Founded by Charles Richter. Logarithmic scale meaning every point is 10 times stronger than the previous, |
| Mercalli Scale. | Measures the damage caused by an earthquake . |
| Short-term effects | Loss of life and injury. Destruction of buildings and communication links. Landslides and avalanches. Tsunamis. Disruption and damage to services. Liquefaction. |
| Long-term effects. | Outward migration. Disease. Economic slowdown. |
| Limiting earthquake damage | Earthquake proof buildings - move with the vibrations: Flexible columns. Rollers. Fire-proofing. Deeper foundation. Cross beams. Reinforced concrete. |
| Nepal earthquake 2015. | What: 7.8 magnitude earthquake. When: 25th April 2015 at 11.56 Where: 77km north of the capital Kathmandu. Dangerous shallow focus. Why: Indian plate overriding the Eurasian plate. |
| Nepal earthquake effects. | 8,000 people killed and 10,000 people injured. Rescue teams could not reach most remote parts. Small villages ruined. 130,000 buildings and homes destroyed. Effect on tourism, avalanches on Everest. 3,000 landslides. Need €1.78 billion to rebuild |
| Japan earthquake 2011. | What: 8.9 magnitude earthquake followed by a tsunami. When: 11 March 2011 Where: 130 km off the east coast of Japan. Why: Pacific plate sinking beneath the Eurasian plate. Part of the Pacific Ring of Fire. Edge of the Eurasian plate jolted back upward |
| Japan earthquake effects. | 27,000 people killed. 90% by the tsunami. Town of 10,000 people destroyed. Fukushima nuclear power plant damaged, state of emergencey. Half a million people homeless. Earthquake caused little damage due to Japans strict building regulations. |
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