Transcript Crustal Movement

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.