Transcript P1 The Earth in the Universe

P1 The Earth in the
Universe
Key Facts
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The universe is 14,000 million years old
The universe possibly started with a big
bang and has been expanding ever since
Our Solar system formed 5,000 million years
ago from dust and gas of old stars
The sun is a ball of extremely hot gas, it’s
diameter is 109 times larger than the Earth’s
A galaxy is a huge group of stars. Our solar
system belongs to the Milky Way galaxy.
Earth
Crust
Only 10-40km
deep
Mantle
Extends half
way to it’s
centre
Core
Made mainly of
iron
Solid at the
centre, liquid
above
Rocks tell Stories!
Deeper layers are older layers, younger rocks
are usually on top
Fossils in the layers show which species lived
when. Many species have become extinct.
Cross-cutting features- if one type of rock cuts
across another rock type, it is younger e.g. hot
magma can fill cracks in existing rocks and solidify
as new rock.
These clues only tell us which rocks are older than others,
not how old the rocks actually are.
Some rocks are radioactive, scientists can estimate their
age by measuring the radiation given off. This is called
radioactive dating.
Rock Cycle
Erosion
What do each of these
Transportation
processes mean?
Deposition of sediment
Compaction and cementation
There must be movement under the Earth’s
surface that changes rocks and lifts land up
to build new mountains.
Otherwise, erosion would wear the
continents flat!
Also, the Earth must be older than the
oldest rocks found here.
Mountains, Volcanoes and
Earthquakes.
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When 2 plates collide, they crumple up
forming mountains.
A volcano is a vent in the Earth’s
surface that erupts magma.
Earthquakes occur when 2 plates slide
past each other causing rocks to
break.
Reducing the Damage
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Educate people.
Organize public drills.
Building regulations.
Prepare emergency plans and train
staff.
Continental Drift
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Wegner’s theory
All the continents were once a single continent,
called Pangaea.
This split up and the continents started moving.
When continents bump into each other they form
mountains.
Earthquakes, volcanoes and mountain building
generally occur at the edges of tectonic plates;
Evidence for this:
1. Mountain chains match up
2. Fossils match up
3. The continents fit together like a jigsaw (not perfect
because of erosion of cliffs!)
Continental Drift
Continental Drift
Some did not agree with Wegener
because;
 The movement is very slow and can
not be detected.
 Wegener was not a geologist.
 Simpler ideas were also suggested
Sea Floor Spreading
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Sea floor spreading is caused by continents
drifting apart forming an oceanic ridge.
They do so at 10cm per year.
Therefore 10cm of rock is produced in the
middle of the oceans every year.
These layers of rock become magnetised in
the direction of the Earth’s magnetic field.
Periodically, the Earth’s magnetic field is
reversed. This causes the rocks at the
bottom of the oceans to be magnetised in
different directions giving it a ‘striped’
appearance.
Why do plates move?
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Solid mantle below Earths crust moves
slowly, moving plates above.
Mantle moves because of convection
currents
Decay of radioactive elements in
the Earth’s core releases energy that
causes these convection currents.
Convection Current
Mountain Formation
Where two continental plates collide, mountains form.
Where two
oceanic plates
are moving
apart and
new sea floor
is being
produced
Sea floor spreading is caused by two oceanic plates
diverging (moving apart from each other). Magma rises up
between the two plates to form new ocean floor (and
sometimes volcanoes). Where new oceanic plate is forming
is called an oceanic ridge.
Seafloor Spreading
Magnetic Stripes
Why do earthquakes happen?
Epicentre of an earthquake
The Solar System
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Formed over a long
period of time, about
5,000 million years ago
Started as clouds of dust
and gas which were
pulled together by the
force of gravity
This created intense heat
leading eventually to
nuclear fusion- star was
born (our sun)
The Solar System
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This consists of the Sun, the Earth, the
moons, the planets, asteroids and
comets.
Asteroids
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Craters are caused by asteroids which
collide with other objects in the solar
system.
This could cause catastrophic
consequences on Earth.
This may have caused a number of
extinctions including the dinosaurs.
The Sun
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The heat and light is caused by nuclear
fusion when hydrogen nuclei fuse to form
helium.
All elements larger than helium were
created in earlier stars.
All stars have a life cycle.
The information we get about other stars
comes from radiation that we can detect.
Life Cycle of a Star
Light
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Light travels very fast, 300,000km/s.
That means that objects far away are
observed as they were a long time
ago.
A light year is the distance travelled in
one year.
Measuring distances between stars is
difficult because of the vast distances.
Measuring Distances
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The distance of stars can be measured
using either:
– Parallax
– Brightness
Movement of Galaxies
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The Sun is a star in the galaxy called
The Milky Way.
There are billions of galaxies in the
Universe, all moving away from us.
The further they are from us the faster
they move away (Hubble’s Law).
This suggests that the Universe is
expanding.
Universe
expands
forever.
Universe
reaches it’s
maximum
size
Universe
collapses
in a big
crunch!
Alien Life
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There are billions of galaxies with
billions of stars, many of which have
planets around them.
Some scientists believe that life may
exist on some of these.
No evidence of alien life has been
detected.
Additional Facts
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Light pollution interferes with
observations of the night sky.
Scientific claims are evaluated by other
scientists by a process called ‘peer
review.’