1. The study of everything on and in the Earth (including the oceans and the atmosphere), and everything outside of it (the universe).
- four major branches
1. geology, the study of the origin, history and structure Earth, and the processes that shape it
2. oceanography, the study of the ocean, including waves, tides, ocean currents and the ocean floor
3. meteorology, the study of the atmosphere and the processes that produce weather
4. astronomy, the study of the universe, including the moon, the planets, the sun and other starts.

2. The Origin of the Earth
The Earth is part of the solar system - a collection of planets and moons, asteroids, comets, and meteorites all orbiting the sun.
Any hypothesis for the formation of the Earth must also explain why…
all planets revolve around sun in same direction
orbits of planets are all nearly circular
orbits are all in nearly the same plane
sun rotates on its axis in same plane as the planets and in same direction as the planets revolve.
most planets rotate in the same direction as the sun
seven of the nine planets have moons
most of the moons revolve around the planets in the same direction as planets revolve around the sun.

3. The Protoplanet Hypothesis aka Nebula Hypothesis - von Weisacher 1944, Kuiper 1950
- explains the origin of the solar system and the earth
5 billion years ago there was a great cloud of gas and dust, 10 billion km in diameter, rotating slowly in space
The cloud was pulled inward due to its own gravitational force
90% of mass moves to center and begins rotating faster
Compressed matter created enough heat that hydrogen fusion began and the sun was formed
10% of mass becomes a plate-like disc
friction → whirlpools or eddies → compact mass into protoplanets
Solar winds blew lighter elements to outer parts of solar system to become outer planets
Heavy elements formed terrestrial planets closer to the sun
rest of material → comets, meteorites, asteroids
earth formed more than 4000 million years ago

4. Formation of Earth  Layers Form on Earth
• As Earth formed, the decay of radioactive elements and heat from high-velocity impacts caused the temperature to increase.
• Lighter rocky components floated outward, toward the surface.
• Gaseous material escaped from Earth’s interior to produce the primitive atmosphere.

5. Atmosphere 78% Nitrogen 21% Oxygen
1% other gases (argon, carbon dioxide, helium)
Early Atmosphere:
- hydrogen, helium
- Escaped into space
Early Atmosphere 2:
- Volcanic eruptions/gases escaping from interior
- Water vapor, carbon dioxide, sulphur dioxide, carbon monoxide, chlorine, nitrogen, hydrogen, ammonia, methane
Early Atmosphere 3:
- Organisms capable of photosynthesis consumed carbon dioxide and produced oxygen

6. Oceans - Hydrosphere - Is nearly 71% of Earth's surface
- Holds about 97% of Earth's water
Meteorites
Volcanic eruptions/gases
Water vapour cooled, condensed into liquid
Dissolved materials from rock added salt content
Collected in lowest areas to form oceans

7. The (mostly solid) Earth; all rock material
- heating causes lighter rock materials rise toward surface.
• crust = lighter rocks, mantle = more dense; iron, nickel and some heavier elements sink to form core
• present continents formed when pressures split apart last super-continent, PANGEA

8. The Earth’s Shape and Size
The Earth is an OBLATE SPHEROID (almost a sphere)
the spinning of the Earth on its axis causes it to bulge at the equator and flatten at its poles
Its surface is relatively smooth –the difference between the highest mountains and deepest ocean trench is only about 20 km.

9. Earth’s Layers
• Based on compositional differences, it consists of the crust, mantle, and core.
- Crust — km thick the thin, dense basaltic rock to lighter granite rock
- Mantle — ~2900 km thick – heavy rock, rich in iron, magnesium and silicon
- Core — ~3450 km thick – outer core (liquid Fe & Ni) – inner core (solid Fe & Ni)

10. Earth’s Temperatures Surface temperatures do not penetrate below 20 m
As you go deeper into the Earth’s crust, the temperature rises about 1°C for every 40 m of depth.
Beneath the crust, this temperature rise gradually tapers off, until a core temperature of about 7000 °C is reached.
The Earth’s heat comes from:
radioactive element decay (uranium, potassium, thorium)
friction between rock masses in the crust and mantle
heat left over from planet formation
The Earth loses heat to outer space very slowly
• Different places on Earth lose heat at different rates due to differences in:
• types of rock (some lose heat faster than others)
• thickness of crust at different locations
• concentration of radioactive elements