Structure of the earth

Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust Outermost layer: Named Lithosphere Lithosphere = crust + upper mantle The crust is only about 8 kilometers thick under the oceans (oceanic crust) and about 32 kilometers thick under the continents (continental crust).

The Mantle The Mantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move. Is responsible for the movement of the Earths plates

The Core Below the mantle and to the center of the Earth. Two Layers of the Core: The Outer and Inner core Contains large quantities of Iron.

The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.

The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.

AND THE THEORY OF CONTINENTAL DRIFT Plate tectonics Mt Everest is getting higher by 7cm every year for the past 35 million years Each time someone climbs it they are actually breaking the record because it’s a little bit higher This is all because of the different plates of the Earth’s crust AND THE THEORY OF CONTINENTAL DRIFT

The Lithospheric Plates Because the plates are ‘floating’ on the asthenosphere, they move around. This movement is responsible for earthquakes and creating valleys and mountain ranges. The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, semi- rigid asthenosphere. Each plate has a name.

Mt Everest getting higher is actually specifically Australia’s fault because the plate we are on is constantly moving north We used to be part of a single plate that contained Australia and Antarctica until it split 65 million years ago (around the time of the dinosaur extinction) Australia is moving north, Antarctica stayed where it was Fossils that are 65 million years old on both Australia and Antarctica are identical, but after that time, they became extremely different There are actually many cases were identical fossils are found on different continents

Distribution of Fossils Plant and animal fossils found on the coastlines of different continents

“Puzzle Pieces” Continents look like they could be part of a giant jigsaw puzzle When Columbus started drawing maps, the Italians realised that all the continents fit together like a jigsaw Then they found other evidence that the continents all used to be joined together

Continental Drift Theory Proposed by Alfred Wegener in 1912 250 million years ago, all of the continents were combined into one super-continent called “Pangaea” The continents gradually drifted apart to where they are today!

Continental Drift

Continental drift flipbook Each map contains an approximate year Start with the most recent and colour each continent in a different colour Work your way back to the oldest map, colouring each landmass in the same colours as the first map Cut out the flipbook along the dotted lines Put the pages in order according to date (oldest on top) Staple the pages on the let side Answer these questions in your book: When does Pangea appear to break apart? When can you identify Laurasia and Gondwana? When can you first recognise North America? Africa? Australia? India?

New Zealand is on two plates, which is why they experience so many earthquakes Australia’s biggest earthquake occurred about 20 years ago at Meckering in Western Australia

Plate boundaries On the map provided, colour each plate a different colour (DON’T USE RED) Name each plate Draw/colour in the location of the Ring of Fire in RED Glue this map into your exercise book Answer the following questions in your book underneath the map Does Australia sit at the edge of a continental plate? Does the location of Australia mean it will be unaffected by plate tectonic movements? Explain your answer.

Plate movement Divergent Convergent Transform Plates are moving apart New crust is created from the cooling magma as it rushes to the surface In continental crust, this creates a valley In oceanic crust, this creates a mid ocean ridge Plates are coming together and one dives under the other Crust is destroyed as it returns to the mantle In a continental crust, this creates a mountain range With 2 oceanic plates or with a continental and oceanic plate, this creates a subduction zone (volcano) Plates are slipping past each other Crust is neither created or destroyed Stress builds up and is released as an earthquake

Divergent Boundaries Boundary between two plates that are moving apart or rifting   RIFTING causes SEAFLOOR SPREADING

Features of Divergent Boundaries Mid-ocean ridges rift valleys fissure volcanoes

Convergent Boundaries Boundaries between two plates that are colliding   There are 3 types…

Type 1 Ocean plate colliding with a less dense continental plate Subduction Zone: where the less dense plate slides under the more dense plate VOLCANOES occur at subduction zones

Andes Mountains, South America

Type 2 Ocean plate colliding with another ocean plate The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH

Aleutian Islands, Alaska

Type 3 A continental plate colliding with another continental plate Have Collision Zones: a place where folded and thrust faulted mountains form.

Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES along faults

San Andreas Fault, CA