1. What are the three plate boundaries, a de- scription of the di- rection in which they move 2. Features of continen- tal plate (4) Features of
... [Show More] oceanic plate (4) 3. What is the structure of the earth starting from the inside (7) 4. Describe what hap- pens at a constructive plate boundary and the landforms associated with it (2) Give one examples of destructive bound- aries 1. Divergent/Constructive (Move away from each other) 2. Convergent/Destructive (Move towards each oth- er) 3. Conservative (Rub against each other) *Continental* - Land on top of shelf - Not so dense: made of granite - Permanent: cannot be created or destroyed - 35-75km thick *Oceanic* - Oceans on top of shelf - Denser: made of basalt - Can be destroyed - 6-10km thick 1. Inner core 2. Outer core 3. Mantle 4. Mesosphere 5. Asthenosphere 6. Lithosphere 7. Crust *Process* 1. Radioactive decay in the core causes convection currents which pulls the two oceanic plates apart. 2. As the plates move apart, pressure is released and magma rises from the mantle to the earth's surface. E.g. Eurasian and North American plates at Mid-At- lantic Ridge *Landforms* 1. Mid ocean ridges e.g. Mid Atlantic Ridge 2. Shield volcanoes e.g. Iceland 5. Describe the formation *Mid-Ocean Ridge* of a mid ocean ridge (Definition + 3 other steps) 6. Define sea floor spreading (Def + 2 oth- er steps) 1. An ocean ridge is a linear belt of mountains where two oceanic plates move apart at a con- structive plate boundary. About 90% of ridges are underwater. 2. Convection currents drag plates away from each other. 3. Pressure is released and magma rises through cracks in the earths crust to fill the gap, pushing the sea floor laterally (Sea floor spreading). 4. As magma cools it builds upper time to form a series of underwater mountain chains as well as a rift-valley in the centre where magma can escape from. 1. Sea floor spreading is the lateral increase of the size of the sea floor as plates move apart at constructive plate boundaries. 2. Magma rises to the surface through cracks in the earths crust and fills the gap. 3. This process occurs at mid ocean ridges where new ocean floor is formed by volcanic activity and then gradually moves away from the ridge as new magma comes to the surface. 7. Describe what hap- pens at a destructive plate boundary and the landforms associated with it (3) Give two examples of destructive bound- aries *Process* Radioactive decay in the core causes convection currents which pushes the plates towards each other. As they move towards each other the more dense plate subducts beneath the other where it melts into the Benioff zone where it becomes molten magma. Can be oceanic meeting continen- tal or oceanic meeting oceanic. E.g. South American and Nazca plates (O/C), Pa- cific and Atlantic (O/O) *Landforms* 1. Fold Mountains (O/C or C/C) 2. Ocean trenches (O/O or O/C) 3. Island arcs (O/O 8. Describe the formation Formation 1 (O/C) Andes: of fold mountains (An- des and Himalayas) 1. Occurs at a destructive boundary. CC moves plates together. 2. Oceanic plate is subducted under continental where it melts into Benioff Zone. 3. During subduction the rocks on the continental shelf are forced upwards due to the large amount of compression when two plates collide. 4. The sediments deposited in the ocean trench are scraped up by the front edge of the continental plate and added to the folded rock. This is called an accretionary wedge. Formation 2 (C/C) Himalayas: 1. Occurs at a destructive boundary. CC moves plates together. 2. Plates move together and as they move they scrape sediments off the floor to form an accre- tionary wedge (Geosyncline) 3. These sediments are crumpled to form fold mountains. 9. Describe the formation 1. The oceanic trenches are long, narrow depres- of ocean trenches (3 steps + an example) sions of the sea floor where one plate subducts beneath the other. They also are the deepest parts of the ocean floor. Can be OC or OO 2. CC push the plates towards each other. 3. The more dense oceanic plate subjects beneath the less dense oceanic plate forming an ocean trench. E.g. Mariana's trench. 10. Describe the formation 1. Island arcs are chains of volcanic islands gener- of island arcs (Def + 4 other steps + exam- ples) 11. What is subduction? What is a Benioff zone? ally in a curved line on the opposing edge of the subducted plate where two oceanic plates meet at a destructive boundary. They are parallel to the ocean trench. 2. Older and denser O plate is subducted beneath the less dense O plate 3. Subducted crust melts in the Benioff zone into molten magma 4. Low density molten magma rises, aided by higher pressure in the mantle and moves through faults and cracks in the thinner plate to create volcanoes 5. A chain of these volcanoes forms an island arc E.g. The Pacific Ring of Fire and Aleutian arc in Alaska Subduction is the process where the denser ocean- ic crust is forced downwards under a continental or another oceanic crust and is melted in the Be- nioff zone. It cannot occur at continental-continental boundaries. 12. What are convection currents? Benioff zone is a zone of melting and earthquakes when a plate has been subducted The movement of mantle due to radioactive decay in the core. Hotter magma rises to crust and falls when it cools, dragging the plates. 13. What are the five types 1. Freeze thaw of physical weathering processes? 14. Describe F T weathering (Physical) (5 steps) 15. Describe H /C weathering (Physical) (5 steps) 2. Exfoliation (Heating/cooling) 3. Salt crystallisation 4. Pressure release (Dilation) 5. Vegetation root action 1. Needs water and temperatures that fluctuate above and below 0 2. Water gets into joints in the rock 3. At night water freezes as the temperature falls and when it freezes it expands by 9%, putting pres- sure on the rock 4. In the day, temperature rises again and the ice melts, so the pressure is released and thawing occurs 5. Process repeats at night again until, eventually, the rock breaks and turns to scree 1. Occurs in deserts. Needs a large diurnal temper- ature range and a very small amount of water/dew. 2. Water helps to conduct heat between the layers of rock. 16. Describe S C weather- ing (Physical) (4 steps) 17. Describe P R weathering (Physical) (3 steps) 18. Describe V R A weathering (Physical) (2 steps) 3. During the day, it's hot, so the outer layers of rock expand quicker than the inside layers 4. At night, it's cold, so the outer layers contract quicker than the inside layers 5. Eventually the layers crack and break off in thin sheets 1. Occurs in deserts where temperatures fluctuate around 26-28 or coastlines where the water is salty. 2. Salts, such as sodium sulphate, are left in cracks when water evaporates to form a precipitate 3. Over time the salt crystals grow and expand which widens the crack (disintegration) [Show Less]