TERRA FIRMA

• crust under the oceans - basalt (more dense)

• crust under the continents - granite (less dense)

• mantle comprises 80% of the earth's volume

• outer core is liquid (molten)

• inner core is solid and is composed of iron, nickel & cobalt which is the source of the earth's magnetic field

• lithosphere - rigid blocks of the crust and upper portion of the upper mantle, also known as the plates, there are 10ish major

plates

• asthenosphere - mixture of solid and molten (plastic-like) rock zone just below the lithosphere, allows the plates to slideCRUST

MOHO

UPPER MANTLE

LOWER MANTLE

OUTER CORE

INNER CORE

there are 3 types of plate boundaries: divergent, convergent and transform faults

in each case the plates are moving at the rate of finger nail growth

earthquakes originate at plate boundaries

at a divergent plate boundary plates move away from each other and create new crustal material

this occurs mostly under the oceans, an exception is the Great Rift Valley in eastern Africa

as the plate split apart a rift zone is created as magma comes up from the mantle

this magma creates volcanoes known as ridges, example mid-atlantic ridge

earthquakes

where plates collide with each other 3 possible results occur due to the type of plate material involved

if ocean plates (basalt) converge both plates will descend into the mantle destroying crustal material

creating a subduction zone

all subduction zones have trenches and as the plate is pushed into the mantle the plate melts and rises to create volcanoes

in this case the volcanoes will form on the ocean floor and with time can extend to above sea level

these volcanic islands are referred to as an island arc

examples of this would be Japan, Mt Pinatubo

earthquakes

if an ocean plate (basalt) converges with a continental plate (granite) the ocean plate will descend into the mantle destroying

crustal material

creating a subduction zone

all subduction zones have trenches and as the plate is pushed into the mantle the plate melts and rises to create volcanoes

in this case the volcanoes will form on the edge of the continent

this volcanic mountain is referred to as a volcanic arc

examples of this would be the Andes, Mt St Helens

earthquakes

if two continental plates (granite) converge neither descends into the mantle

folded mountains result

examples of this would be the Himalayas, Alps

earthquakes

transform faults are where 2 plates slide past each other horizontally

the only result are earthquakes, no mountains are created

an example of this is the San Andreas fault