Inside the Earth

Why does the earth look the way Why does the earth look the way it does today?it does today?

• http://www.youtube.com/watch?v=p0dWF_3PYh4

2 ways to describe layers: Composition, Physical Properties

Composition (What it is made of)

• Crust – outer layer, thin, broken into tectonic plates

• Mantle – middle layer, thick, convection currents from heat of earth’s core movement of Earth’s plates

• Core – middle, very hot, dense

Physical Structure of the Earth(5 Layers)

• Lithosphere- rigid outer layer (crust)

• Asthenosphere- solid rock that flows slowly (like hot asphalt)

• Mesosphere- middle layer

• Outer Core- liquid layer

• Inner Core- solid, very dense

Why does the earth look the way Why does the earth look the way it looks today?it looks today?

Theory of Plate TectonicsTheory of Plate Tectonics

Earth’s surface = about a dozen major rigid, moving crustal plates +several smaller plates

PlatesPlates

- Slabs of Earth’s lithosphere (crust + upper mantle)

- Average thickness ~ 100 km (62 miles)

- Most support both continent and ocean

Continental DriftContinental Drift – states that the continents have drifted and still are drifting apart.

Animated Plate Tectonic Reconstruction

Why do the plates move?

1. Tremendous heat in asthenosphere

2. Plates “ride” on hot, flowing rock

3. Plates move b/c heat is released from deep inside earth.

4. Convection currents cause hot material to rise and expand (plates diverge) and cooler material to sink and contract (plates converge).

http://www.wisc-online.com/Objects/ViewObject.aspx?ID=SCE304

Alfred WegenerAlfred Wegener – proposed that in the distant past, the Earth’s continents were all joined as a single landmass.

Evidence for Wegener’s theory

a. South America + Africa fit like a puzzle

b. Match of ancient continental rocks and tectonic (fold & fault) structures in Americas and Africa/Europe.

c.c. PangaeaPangaea – hypothetical “super continent” made of all current continents

d. Fossil evidence

Fossil Evidence

What do you think of this theory and the evidence behind it?

Turn and talk with the people at your table to discuss the strengths and weaknesses of Wegener’s ideas

• Divergent

• Convergent

• Transform

Three types of plate boundary

Day 2 – Why does the earth look the way it does today?

• What forces are at work that we cannot see?– Convection currents in the mantle

• We saw this yesterday: http://www.wisc-online.com/Objects/ViewObject.aspx?ID=SCE304

• http://www.youtube.com/watch?v=gFU9n_GhsdM

• How would this motion affect plate tectonics?– http://www.youtube.com/watch?v=p0dWF_3PY

h4

• Divergent

• Convergent

• Transform

Three types of plate boundary

• Spreading ridges– As plates move apart new material comes up to fill the

gap

Divergent Boundaries

• Iceland has a divergent plate boundary running through its middle

Iceland: An example of continental rifting

Oceanic-oceanic divergent• Effects: Magma rises to surface & cools

mid-ocean ridges, volcanic activity, shallow earthquakes, sea-floor spreading

• Example: Mid-Atlantic ridge

Continental-continental divergent• Effects: Rift valleys, sometimes with lakes

or shallow oceans, shallow earthquakes, occasionally volcanoes

• Ex: Rift valley of East Africa

• There are three styles of convergent plate boundaries– Continent-continent collision– Continent-oceanic crust collision– Ocean-ocean collision

Convergent Boundaries

• Called SUBDUCTION

Continent-Oceanic Crust Collision

Oceanic-continental convergent• Effects: subduction, earthquakes, ocean

trench, line of volcanoes

• Examples: Andes mountains in South America

• When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone.

• The bottom plate bends down to form a trench.

• The world’s deepest parts of the ocean are found along trenches. – E.g. The Mariana Trench is

11 km deep!

Ocean-Ocean Plate Collision

Oceanic-oceanic convergent• Effects: earthquakes, ocean trenches, chain

of volcanic islands

• Ex: Japan

• Forms mountains, ex. European Alps, Himalayas

Continent-Continent Collision

Continental-continental convergent

• Effects: Mountains, shallow earthquakes

• Example: Himalaya mountains in India

Himalayas

• Where plates slide past each other

Transform Boundaries

Above: View of the San Andreas transform fault

Transform plate boundaries

• Effects: lots of earthquakes and faulting

• Example: San Andreas fault in California

Earth on the Move

Earth Structure & Plate Tectonics Notes

Earth, Inside & Out

• The Earth is divided into three layers

1. Crust 2. Mantle3. Core

Crust • (1)  This is the outermost

layer of the Earth.• (2) This is the layer we walk

on.• (3) It is a thick, rocky skin.• (4) If we think of the Earth as

a pool ball, this crust is as thin as a postage stamp stuck on a pool ball.

• (5) At its thickest, which is under mountain ranges, the crust is only about 35km (22mi) thick.

And what type of crust would you like with your

Earth?

• There are two types of crust

Continental Crust:

• 1. Makes up the continents

• 2. Contains light colored rocks such as granite.

• 3. Floats high on the mantle

    Oceanic Crust

• 1.       Makes up the ocean floor

• 2.     Contains the dense rocks such as basalt

• Thinner than the continental crust

Mantle

• (1)  Hotter and denser than the crust because the deeper you go inside the earth, the temperature & pressure increases.

• (2) Made of solid rock.

• The Mantle is made of two zones

Mantle Zones

• (a)  Lithosphere• (i)    Thin, uppermost part

of the mantle; cooler & less rigid

• (ii) Floats on the athenosphere, and slides around very slowly.

• (iii)  The upper part of the lithosphere melts rocks, forming a substance called magma.

Magma

• 1.  Magma (melted rock) moves like hot oatmeal.

• Uneven heating causes material in the mantle to constantly and slowly rise & fall in convection currents.

• Convection Current: process by which hot fluid rises to the surface, and then sinks again, like soup being heated in a saucepan

Asthenosphere

• Hot, weak zone directly under the lithosphere

• Flows at a very slow rate

Core

• i)       Deep within the Earth is the core

• ii)    The core is made mostly of nickel & iron

• iii)  Twice as dense as the mantle.

• Main source of heat that triggers the convection currents

The core is made of two layers

• (1)  Outer core: molten & is responsible for the Earth’s magnetic field.

• Inner core: solid