Paper 1- Dynamic Landscapes Flashcards
Pahoehoe Lava
Thin, fast flowing lava, cools to form a wrinkled surface
AA/Blocky Lava
Thicker Lava, flows slowly and cools to form a jagged surface
What is the distribution of natural disasters
Natural disasters occur on plate boundaries
4 types of plate boundaries
Divergent, Convergent, Collision, Transform
What are hotspots and how do they form volcanic island arcs
Hotspots: Intra-plate location where magma from mantle breaks through a weak point in crust
1) Radioactive decay of material in mantle
2) Mantle superheats and plume of magma forms through the mantle and the lithosphere
3) Crust breaks open and volcanoes form
4) As a plate moves, volcanoes move away from the mantle plume in the direction of the plate movement, and a new shield volcano forms in it’s place, creating volcanic island arcs.
Example: Hawaii
Why are converging plate boundaries highly destructive?
Lava is thicker and contains more silica, preventing gas from escaping, causing pressure to build up and release all at once, causing severe damage.
What are faults?
Cracks in the Earth’s surface.
What are Rift Valleys and how are they formed?
Rift Valleys: Elongated troughs formed by divergent plate boundaries. (Either continental or oceanic)
1) Crust extends in 2 different directions due to upwelling magma pushing asthenosphere into lithosphere, causing crust to thin, bend and fracture.
2) This leads to the formation of faults, fractures in the crust where one section of rock sinks and the rock surrounding remains.
3) These trough like sections are called grabens. The parts of elevated rock are called horsts.
Examples: Mid Atlantic Ridge, African Rift Valley
Rift Valleys can cause significant volcanic activity.
explain the process of convection currents
Due to the decay of radioactive elements, convection currents move the plates when the hot magma rises and cool magma sinks, new science disproves this, seeing as convection currents move slower than tectonic plates
explain slab pull
as a plate moves further from an oceanic ridge it cools and becomes dense, causing it to sink, creating a major pulling action which causes the rest of the plate to get pulled down as well.
ridge push
molten magma that rises heats the rock around it.
The asthenosphere and lithosphere expand and become elevated.
This produces a slope away from the ridge. The magma forms hot rock, making it less dense than the rock away from the ridge.
As it cools it gains density and gravity forces it to slide away from the ridge.
as the old lithosphere slides away, new magma wells up, forming the new lithosphere.
