P1 The Earth in the Universe - PowerPoint

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					P1 The Earth in the
Key Facts
   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

                Extends half
                way to it’s

            Made mainly of
            Solid at the
            centre, liquid
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
Transportation             What do each of these
Deposition of sediment     processes mean?
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
   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
Reducing the Damage

   Educate people.
   Organize public drills.
   Building regulations.
   Prepare emergency plans and train
Continental Drift
   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
   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
 The movement is very slow and can
  not be detected.
 Wegener was not a geologist.

 Simpler ideas were also suggested
Sea Floor Spreading
   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’
Why do plates move?

   Solid mantle below Earths crust moves
    slowly, moving plates above.
   Mantle moves because of convection
   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

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
   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

   This consists of the Sun, the Earth, the
    moons, the planets, asteroids and

   Craters are caused by asteroids which
    collide with other objects in the solar
   This could cause catastrophic
    consequences on Earth.
   This may have caused a number of
    extinctions including the dinosaurs.
The Sun

   The heat and light is caused by nuclear
    fusion when hydrogen nuclei fuse to form
   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 travels very fast, 300,000km/s.
   That means that objects far away are
    observed as they were a long time
   A light year is the distance travelled in
    one year.
   Measuring distances between stars is
    difficult because of the vast distances.
Measuring Distances

   The distance of stars can be measured
    using either:
    – Parallax
    – Brightness
Movement of Galaxies

   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

reaches it’s

 in a big
Alien Life

   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
Additional Facts

   Light pollution interferes with
    observations of the night sky.
   Scientific claims are evaluated by
    other scientists by a process called
    ‘peer review.’