Download Evidence for continental drift - Mamanakis

Origin of the Universe
Origin of Universe
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Big Bang model (Hubble, 1929) - The
universe began with an explosive
expansion of matter, which later became
what we know as stars, planets, moons,
etc. This event is thought to have
occurred 10 - 15 billion yrs ago.
Nebular Hypothesis (Kant, Laplace
1796) - Earth and the other bodies of
our solar system (Sun, moons, etc.)
formed from a “vast cloud of dust and
gases” called a nebula.
Big bang theory
•There was a big bang some 15 billion
years ago, when the size of the universe
was zero and the temperature was infinite.
The universe then started expanding at near
light speed.
•At about 10,000 years after the Big Bang,
the temperature had fallen to such an extent
that the energy density of the Universe
began to be dominated by massive
particles, rather than the light and other
radiation which had predominated earlier.
This explains the formation of galaxies and
other large-scale structures observed in
universe today.
Nebular Hypothesis
•According to this hypothesis,
the nebular cloud consisted of
H and He, and a small
percentage of the heavier
elements we find in the solar
system
•Within the rotating disk, the
rocky material and gases
began to nucleate and accrete
into protoplanets
Formation of Earth’s Interior
•As Earth was formed, it was extremely hot
from the bombardment of space debris,
radioactive decay, and high internal pressures.
•These processes caused Earth’s interior to
melt, and then to differentiate into regions of
chemical and physical differences as it
cooled.
Continental drift
Theory
that continents and plates move
on the surface of the Earth proposed by
Alfred Wegener in 1915.
Alfred Wegener
Maps by Wegener (1915), showing
continental drift
Theory of continental drift
Evidence for continental drift
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Matching coastlines
Matching mountains
Matching rock types and rock ages
Matching glacier deposits
Matching fossils
Evidence for continental drift
Matching
coastlines
Evidence for continental drift
Matching
mountain
ranges
Evidence for continental drift
Matching
rock types
and ages
of rocks
Evidence for continental drift
Matching glacier
deposits 300
million years
ago
Evidence for continental drift
Fossils of of Mesosaurus
(aquatic reptile) found on
both sides of Atlantic
Theory of Plate tectonics
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The theory of Plate tectonics was proposed in
1960s based on the theory of continental drift.
This is the Unifying theory that explains the
formation and deformation of the Earth’s
surface.
According to this theory, continents are carried
along on huge slabs (plates) on the Earth’s
outermost layer (Lithosphere).
Earth’s outermost layer is divided into 12 major
Tectonic Plates (~80 km deep). These plates
move relative to each other a few centimeters
per year.
Earth’s magnetic field
Basic Data used in
formulating plate tectonics:
Magnetic stripes on the seafloor. Magnetic field of
Earth reverses on semiregular basis. Minerals act
like compass needles and
point towards magnetic
north. “Hot” rocks record the
direction of the magnetic
field as they cool.
Tectonic plates of Earth
Types of plate boundaries
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Divergent plate boundaries: where plates
move apart
Convergent Plate boundaries: where plates
come together
Transform plate boundaries: where plates
slide past each other
Types of plate boundaries
Divergent (Tension)
Convergent (Compression)
Transform (shearing)
Types of plate boundaries
What drives plate movement?
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Ultimately: heat transported from core and
mantle to surface
Heat transported by convection
Core is ~5,000°C and surface is ~0°C
Where mantle rises: rifting
Where mantle dives: subduction zones
What are Seismic Waves?
Presentation based upon information retrieved from: http://www.geo.mtu.edu/UPSeis/waves.html
Movie clips from United Streaming
Seismic Wave
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Seismic waves are the waves of energy caused
by the sudden breaking of rock within the earth
or an explosion. They are the energy that travels
through the earth and is recorded on
seismographs.
There are several different kinds of seismic
waves, and they all move in different ways. The
two main types of waves are body waves and
surface waves.
Earth Stats
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The Earth's mass is about 5.98 x 1024 kg.
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Earth is the densest planet in our Solar
System (mass/volume).
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Earth is made of several layers with
different compositions and physical
properties, like temperature, density, and
the ability to flow.
The Composition of the
Earth
The Composition of the
Earth
Crust
•Thinnest layer (5-100 km)
•Two types of crust
•Continental
•Like granite
•Average 30 km
•Oceanic
•Like basalt
(Basalt is denser than granite!)
•Average 5-8 km
The Composition of the
Earth
Mantle
•Extremely Thick! (2,900 km)
•It is too far down to drill
•How do we know what it is
made of?
•Scientists infer based on:
•Pushed up rock
•Ocean floor/molten rock
•What is it like?
•Like the mineral olivine
•Large amounts of iron and
magnesium
www.soc.soton.ac.uk
The Composition of the
Earth
N
Core
•Pretty darn big. (6,856 km)
•(Slightly bigger than Mars!)
•33% mass of the Earth
•Scientists think….
•Made mostly of iron
•Some nickel, sulfur, oxygen
•What is the evidence?
•The particular way seismic
waves travel
•Earth’s Magnetic field
S
The
Structure of
the Earth
Lithosphere
Solid
Asthenosphere
Viscous Liquid
Outer Core
Liquid
Mesosphere
Solid
Inner Core
Solid
Lithosphere = ‘rock sphere’
Crust and upper rigid part of Mantle
Asthenosphere = ‘weak sphere’
Lower part of Mantle
How HOT is it?
Mystery Box
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Do we know for sure