Crustal Movement

Layers of The Earth

• Core – Center of the earth– Contains Iron and Nickel– Two Levels

• Inner Core – Solid– Yes there is tremendous heat but it is out weighed by

the enormous pressure which pushes the particles of Iron and Nickel so close together that they remain solid.

• Outer Core – Liquid– Here heat out weighs the pressure and the Iron and

Nickel are molten

Mantle

• Middle layer of the Earth

• Comprised mostly of silicon, oxygen, iron, and magnesium.

Crust• Solid and rocky outer layer of the earth

– Think of the crust like an apple peel – very thin outer layer.

– Types• Oceanic – Crust beneath the ocean

– Comprised of silicon, oxygen, iron, and magnesium

• Continental – Crust beneath the continents– Comprised mostly of silicon, oxygen, aluminum,

calcium, sodium, and potassium.

Crust • Levels

–Lithosphere• Solid topmost part of the Earth

–Asthenosphere• Often considered to be the upper edge of

the mantle–Made of molten material–Property of Plasticity

»Able to flow or move easily

Activity

• Draw your own version of the Earth’s Layers

Plate Tectonics

• Continental Drift Theory–Alfred Wegener

–1912

Plate Tectonics• Continental Drift

–The Theory• All of the continents were once joined in

one large land mass, Pangaea, that began breaking up and drifting apart millions of years ago

• Wegener’s theory was very unpopular and rejected by most of the world’s scientists.

Plate Tectonics

• Continental Drift– The Evidence

• Identical types of fossils were found in Africa and South America

• Many of the Earth’s rock formations line-up with formations on other continents.

– Mountain ranges in African line up with matching ones in South America.

– Coal fields with distinct layers in Brazil match up with identical fields in Africa

Plate Tectonics

• Continental Drift–The Evidence

• Glacial Deposits (Sediments and Rocks left behind by glaciers) have been found in South America, Africa, India, and Australia.

• The Continental coast lines fit together like the pieces of a puzzle.

Plate Tectonics

• Sea-Floor Spreading–Harry Hess

–1960

Plate Tectonics

• Sea-Floor Spreading–Discovered a large system of

underwater mountains.• Contain a deep crack

–Lava erupts through these cracks pushing the ocean floor on either side away.

–The lava hardens and forms new ocean floor.

Plate Tectonics

• Sea-Floor Spreading– The evidence

• Samples have shown that the further away from a ridge you get the older the rock.

• Magnetic memory of rock material in the ocean– As magma hardens at ridges half of the rock

moves in one direction and half moves in the other.

» On each side the magnetic strips match the earth’s magnetic pull.

Plate Tectonics

• Plate Tectonics–J. Tuzo Wilson

- 1965

Plate Tectonics• Plate Tectonics

–Plate• The moving, irregularly shaped slabs that

fit together like paving stones to form the surface layer of the earth

–Tectonics• The branch of geology that deals with the

movements that shape the earth’s crust

Plate Tectonics• Plate Tectonics

– The Theory• The earth’s plates are in constant, slow

motion, driven by convection currents in the mantle.

– Do you know what convection is?

• Seven Major Plates– Named for the area its surface features.

» For example – The Pacific Plate

• Can move up to several centimeters per year.

Plate Tectonics

• Plate Tectonics–Convection

• Hot material rises from the core and cool material sinks towards the core.

• The cool material then heats and the rises this circular cycle causes movement.

Activity

• Draw your own model of convection currents.

Plate Tectonics

• Plate Tectonics –Plate Boundaries

• The points where plates meet.–3 Types

»Divergent»Convergent»Transform or Strike-Slip

Plate Tectonics

• Plate Tectonics– Divergent

• Move apart at mid-ocean ridges.

Plate Tectonics

• Plate Tectonics– Boundaries

• Convergent– Plates come together at trenches – One plate moving

over top of the other.

Plate Tectonics

• Plate Tectonics – Boundaries

• Strike-Slip– Two plates grind together and slip past each other

horizontally. No new material is created and none is destroyed.

Geological History

• Fossils–Preserved remains or traces of living things

–Can be used to determine age.

Geological Time Scale

• Fossils–Law of Superposition

• In horizontal sedimentary rock layers, the oldest rock is on the bottom

Geological History• Fossils

–How do you think Paleontologist determine the age of fossils?• Radioactive (Carbon) Dating

–Determines the absolute age of rocks and fossils.

–The rate at which a radioactive element decays is a constant.

»Half Life

Geological History

• Fossils–Index Fossils

• The remains of plants and animals that existed for a relatively short period of time in a wide area.

• Tell the relative age of rocks

Geological History

• Geological Time Scale– Eras – Plaeozoic, Mesozoic, Cenozoic– Periods – Eras are divided into periods.– Epochs – Only in the Cenozoic period

because the information we have for this era is so much more complete.