5.2 theory of plate tectonics

conservative margin?

where 2 crustal plates slide past eachother to relieve stress due to the shifting crust

how is the crust destroyed?

melting back into magma at the convergent margin where it subducts

subduction

when one plate is forced beneath another into the mantle

why doesn’t the earth get bigger?

because where one part of the earth moves apart, the other plate subducts and melts back into magma

what does conservative margins produce?

earthquakes

what does divergent margins do?

move apart which allows magma to rise and new crust to form

what does divergent margins produce?

volcanic activity

convergent boundaries

through subduction where it melts into the mantle and recycles for the divergent

mantle

thick layer of rock between the earths crust and its core

Asthenosphere

located below the lithosphere its semi-fluid which allows the tectonic plates to move on top of it

whats the temp of the inner-core?

the same as the surface of the sun

who created the theory about continental drift? (CD)

Alfred Wegener in 1912

the continental drift? (CD)

believed that 300 million years ago there was a single continent called ‘Pangaea’ and that they split into 2 continents and began drifting until they got to where they are today.

what is the core made of?

dense rock containing iron

residual primordial heat

leftover from the earths formation

how deep is the upper mantle?

from the crust to about 410km

how much of the earths volume is the upper mantle?

84%

characteristic of the upper mantle?

mostly solid with some malleable regions which contribute to tectonic activities

sea floor spreading

new crust forming as plates move apart

what are the 2 parts of the upper mantle? (known as layers)

lithosphere (crust)

Asthenosphere

how deep is the transition zone?

from 410-660 km

how does crust vary?

thickness

what are the 2 main categories for plates?

oceanic

continental

what does the lithosphere consist of?

crust & upper section of the mantle

what are the 2 continents Pangaea split into?

Laurasia

Gondwana

limitations to Wegener’s continental theory?

he didn’t know how the continents moved

how does the earths continent move?

by floating on the semi-fluid asthenosphere

an example of evidence that supports CD

there are striations on rocks in Brazil and West Africa which suggests that they formed together, then moved

example of biological evidence of CD

fossil remain of the reptile Mesosaurus are found in both south America and South Africa. its unlikely they developed in the same area or crossed the Atlantic so it must be the movement of continents

how does convection move tectonic plates?

by a ‘dragging’ movement

an example of a conservative margin?

San Andreas fault in California

what are conservative margins also known as?

transform boundaries

what does the UNDRR do?

focuses on reducing disaster risks globally and implementing the Sendai framework which aims to make communities more resilient to disasters

what does FEMA do?

responsible for coordinating the response to disasters that overwhelm state and local authorities.

what is the depth of the Marianas trench?

11 km