The Restless Earth Flashcards
What are the 4 layers of the earth?
Crust (solid)
Mantle (mostly solid)
Outer core (liquid)
Inner core (solid)
What are the two types of crust?
What are their differences?
Oceanic.
Very dense (mean density is 3000kg/m3)
Thin 5-10km
Can sink into mantle
Easily destroyed
Young crustal material
Continental.
Less dense (mean density is 2,700kg/m3)
Thick 30-70km
Does not sink easily into the mantle
Hard to destroy
Old crustal material
What are the 13 tectonic plates?
(Use a diagram)
1 North American plate
2 Pacific plate
3 Nazca plate
4 South American plate
5 Cocos plate
6 Caribbean plate
7 African plate
8 Eurasian plate
9 Arabian plate
10 Indian plate
11 Australian plate
12 Philippine plate
13 Antarctica plate
What makes plates move?
Convection currents
What is Pangea?
250 million years ago, a supercontinent slowly broke up and drifted apart creating the continents as we know them today.
What are the four main types of plate margins?
Constructive
Destructive (oceanic + continental or oceanic + oceanic)
Collision
Conservative
What happens at a constructive plate boundary?
Plates are pushed apart, so they move away from one another and new crust is created. Magma wells up from the mantle to plug the gap, so there is often frequent volcanic activity here. This movement causes regular, but weak earthquake activity.
The rising of material pushes up the crust slightly at either side of a plate margin, thus creating a mid-oceanic ridge
Mid Atlantic ridge (in the Atlantic Ocean). Here, the North American and Eurasian plates are being pulled apart, moving away from one another.
What happens at a destructive plate boundary? (Oceanic + continental)?
Where an oceanic plate crashes into a continental plate and the oceanic crust is pushed into the mantle and destroyed. This movement is not smooth, because of the friction between the rough surfaces. The plates may become stuck until pressure is suddenly released, causing an earthquake.
When the heavy oceanic crust is pushed downwards into the mantle it creates a deep ocean trench.
Peru-Chile trench - this has been created where the Nazca plate (oceanic crust) is disappearing below the South American plate.
What happens at a destructive plate boundary? (Oceanic + oceanic)?
Where an oceanic plate crashes into another oceanic plate. As the oceanic crust sinks into the mantle it melts and creates a less dense material than the surrounding rock.
When the heavy oceanic crust is pushed downwards into the mantle it creates a deep ocean trench. Magma may also rise up and erupt through the crust to create an arc of volcanic islands.
Mariana ocean trench in the Pacific Ocean.
What happens at a collision plate boundary?
Two sections of continental crust crash into each other. The crusts both plates buckle and fold upwards
When the continental plates collide, fold mountains are formed (as both plates are the same density). The two sets of mountains overthrust one another, creating a large range of high mountains.
Himalayas and the Andes
What happens at a conservative plate boundary?
Plates slide past each other. Crust is neither created or destroyed. When friction causes the two plates to sick, pressure to move builds up. This pressure is eventually released as an earthquake when the plate move suddenly.
No landforms. As crust is neither creates nor destroyed at conservative margins, there are no volcanic eruptions.
San Andreas fault in California.
What are the shield volcano characteristics?
Large, wide, cone shaped volcanos with gentle slopes. Made from layers of runny lava flows.
Give some examples of shield volcanos
Mauna kea in Hawaii
Galápagos Islands.
What are the characteristics of a composite volcano?
Tall, mountain shaped volcanos made of hardened ash and lava. Often have multiple vents.
Give some examples of composite volcanos.
Helka in Iceland
Mt St Helans in USA
Mt Kilimanjaro in Tasmania.
