Download 3202 INTRODUCTION

WORLD GEOGRAPHY
3202
INTRODUCTION
The Size of the World
The Earth’s Interior
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Crust (Lithosphere)
Mantle
Outer Core
Inner Core
Inner Core
• The deepest part of the
earth (1512 miles deep) is a
solid that contains both iron
and nickel.
• It is because of this that the
center of the earth is a
magnet, a compass.
• It generates a magnetic
field that protects the earth
from flying out of orbit.
Outer Core
• Outside of the inner core
lays the outer core (1419
miles deep).
• This is much like the
inner core with the
exception that it is a
liquid that contains
sulphur and oxygen
(which lowers the melting
point).
Mantle
• Occupying 1789 miles of
the earth is the magma
(iron and magnesium)
that makes up the
mantle.
• Upper and lower
• It is extremely hot!!
• goopy; very plastic-like.
(upper mantle)
• Mostly solid (lower
mantle)
Crust
• Also called lithosphere
• This is the top layer of the
earth, which is basically
hardened mantle
(magma).
• It contains two segments,
the oceanic and
continental crusts.
• Note: this is the same
crust, it just depends how
thick it is to determine if
it is part of the Oceanic or
Continental Crust.
Read About Earth’s interior
• Our Text p. 4-6
Theory Of Continental Drift
• Alfred Wegener
• It is this German man to whom we
credit with the proposal of the
theory of Continental Drift.
• While pondering the
similarities between
the coastlines of
South America and
Africa, Wegener
came up with an
idea:
• What if the
continents were once
all connected and
just drifted over the
years?
Wegener’s Proof
Wegener’s Proof
Wegener’s Proof
The Flaw in Wegner’s Theory
• He thought that each of the continents were a
separate plate--they were just drifting on a neverchanging ocean.
• Like styro-foam floating on a pool of water!!
Missing Proof
• Wegener could not explain what mechanism
was powerful enough to move huge
continents
• Scientist’s never believed him
Canadian Correction
• J. Tuzo Wilson
• the 1960’s Canadian scientist who
resurrected Wegner’s theory after years of
disbelief by the science community.
• Today, we know that that's false, thanks to
the discovery of crustal plates.
• The plates of the earth are not composed of
just land; they're composed of ocean too.
Canadian Correction –
cont’d
• In some cases, the plates are just land, in
others they're just ocean, and, in still
other cases, they consist of land and
ocean.
• They each have different boundaries and
move in all different directions.
Plates of the earth p. 12
Continental Drift Animation
Continental Drift
• refers to the movement of
the more than 20 plates (9
major) due to convergent,
divergent, and transform
boundaries.
• The continents drift at a
rate of 2 inches a year.
• Started 200 million years
ago
• Pangea (land) & Panthalasa
(sea)
Plate Tectonics
• Tectonic plates move or float on top of the
upper mantle.
• However they do not float freely.
• The plates are forced in specific directions
by the flow of magma beneath.
Plate Tectonics – cont’d
• Plates move with the flow of magma.
• The magma closer to the core heats and then rises
towards the surface as its density decreases.
• Once the rising magma reaches the lithosphere it
moves in opposite directions.
• The magma forms convectional currents.
Convection Currents
Plate Tectonics – Convection Currents
Divergent Boundaries
• Tensional Forces occur where two tectonic plates are
pushed apart. The tension is created as the plates move
away from each other.
• Ridge Zones sometimes occur where two plates move
apart. The magma rises between the plates and forms a
ridge.
• Again caused by convectional currents in the magma
Tensional Forces – Ridge Zones
This diagram above shows “Sea Floor Spreading”
Where’s the TENSION?
Convergent Boundaries
• Compressional Forces occur where two tectonic
plates come together. They compress against each
other.
• Subduction Zones sometimes occur where
compressional forces result from two plates
colliding and one plate slips under the other.
• Again caused by convectional currents in the
magma
Compressional Forces – Subduction
Where’s the Subduction / Compression?