- First formed earth was completely molten
- earth 4500 million years old
- oldest rocks 4000 million years old
- Studying rocks tells us about earth structure. We can see-
- Erosion ( caused by weathering to make compact levels of sedementry rock)
- Craters ( astroids crashing to earth)
- Mountain formations ( edge of tectonic plates)
- Folding (of rocks, caused by a large force over time, rocks appear like they have been folded in half)
The Structure of the Earth
- Thin Rocky Crust ( Crust varies between 10 km and 100km, oceanic crust lies beneath oceans and land crust formes continents
- The Mantle (Extends to almost half way to the core, high density and different composition the the crust and is hjot under pressure)
- The Core(Over half of the earths radius, made of nickel and iron, keeping the centre of the earth hot.
- Wegeners Theory
- Saw that continents had a jigsaw fit with mountain ranges and rock patterns matching up
- Also fossils of the same types of animals found on two different continents.
- Claimed also that that when two continents collided they produced mountains
- However geologists did not believe him because:
- He was not a trained Geologist
- Supporting evidence was limited
- The fossils could be explained in a different way ( land bridges)
- The movement of the continents was not dectectable at the time
- See floor spreads 10 cm per year
- The earths crust is cracked into several large pieces called tectonic plates or continents as we know them
- The boarders of these plates are called plate boundaries. Volcanoes and mountains usually occur on these boundries
- Earthquakes near the sea
A geohazed is a Natural hazard
- Earth quakes
Some of the geohazards have warnings like weather pattens however earthquakes have no warning and so we can only do little things to help.
In earthquake zones ( Japan) we build flexiable buildings so that the damage is reduced. Where flooding is known no one is allowed to build.
Convection currents in the mantle cause the magma to rise. The currents move the solid bit of land above it. Where the plates move apart liquid magma rises and solidifies turning into rock.
Earth has a magnetic field it changes every million years. with sea floor spreading it produces rock stripes of alternating poalarity. Geologists can see how quickely a crust is formed by looking at the width of the stripe.
The Solar System
Formed about 5000 million years ago
Started as dust and gas clouds pulled by gravity
Nuclear Fusion began and the sun was formed
Smaller masses are:
Comets ( ice + rock)
Asteroids ( rock )
Sun and Universe
The sun is 500 million years older then earth
Suns energy = nuclear fusion
Nuclei of hydrogen atoms that fuses together during nuclear fusion.
The Universe is aprox 14000 million years old
Speed of light
light from the earth to the moon takes just over 1 second
Sunlight takes 8 minutes to reach earth