Global distribution and causes of earthquakes, volcanic eruptions and tsunamis

Lithospheare

The upper part of the mantle and crust combined

Asthenosphere

The semi molten area of the mantle that excludes the upper rigid alter mantle

Tectonic plates float on this

Features of The crust

The outer layer of the Earth

0-100 km thick

Includes continental and oceanic crust

Features of the mantle

2900 km thick

Semi molten magma

Convection current

Upper mantle hard rock lower mantle is soft and beginning to melt

The outer core

Semi Molten

4500 to 6000°C

Liquid iron And nickel

2250 km thick

The inner core

• hottest part of the Earth

• 6000°C +

• Solid iron and nickel

• 12,000 km thick

Features of a continental plate/crust

• Thickness – 35 to 50 km

  • 70 to 60 km on mountain chains

• Age – Old and 15,000+ million years old

• Density – lighter Average density of 2.7 g/cm³

• Composition– Mainly silica and aluminium and Granite is the most common rock

Features of the oceanic plates/crust

• thickness – 6 to 10 km average

• Aged – very young Under 700 million years old

• Density – heavier average density of 3.0 grams per centimetre cubed

• Composition – mainly silica and magnesium and basalt is the most common rock

Alfred Wegner - Continental drift

• suggested the worlds landmasses were once joining together as Pangea (Supercontinent)

• They then split into two landmasses ‘ Laurasia’ And ‘Gondwanaland’

• Evidence was that coastlines fit together

• Fossil records - Maurus southern Africa and Brazil

• Rock distribution was similar in the USA in UK

Harry Hess- Seafloor spreading

• Ocean shallow in the middle and found the deepest part of the ocean were very close to continental margins

• Ocean grow From their centres with basalt are oozing up from the mantle along the ocean ridges

Convection currents

• radioactive decay creates extreme heat energy (Unstable isotopes in the core)

• Energy is transferred to the mental cause it to rise the rising magma then calls sideways under the crust and falls back down

• Where convection currents diverge and plates move apart

• Where they converge is where plates move together

• The Arctic Ridge has the slowest rate of convection current less than 2.5 cm per year

Slab pull

• newly formed ocean plates move away from a constructive margin

• It cools and becomes denser and sinks into the mantle

• It occurs when an oceanic plate abducts and pull the rest with it

• The Wadati-Benioff zone Is the passing into the mantle taken by the plate being subducted and is seismically active

• High levels of friction can be held and cause locked fault (Movement stops)

• The harsh release can cause earthquakes

Seafloor spreading

• Play it move away from each other forming New oceanic crust

• The main driver of this movement is gap filling

• Every 400 years or so The Earth magnetic field changes direction

• The minerals lineup with the north south pole which shows the polarity at the time

Summary

• Continental crust does not sink due to low density making it permanent

• Oceanic crust is constantly being destroyed and created

• Continental plates can be both continental and oceanic, e.g. Eurasian plate

• Plates cannot overlap nor have gaps between them

• Earth is not expanding or shrinking

• Movement is slow faster movement causes earthquakes

• Most significant landforms are at plant margins