Earth Science

[Jessica]

Four realms of Earth
1. Geosphere: the solid Earth
2. Hydrosphere: the water around us
3. Atmosphere: the air
4. Biosphere: life on sea, land, and air


Geosphere: Largest realm. Earth’s radius~ 6400 km

Three major layers in Geosphere:

1. Crust: Outermost very thin layer. Hard or soft rocks of various colors (Fig. 1-3) beneath soil or ocean water. About 5-65 km (3-40 mi) thick. Similar to skin on apple.

2. Mantle: Composed mostly of solid rocks and pools of hot liquid rocks (magma). Largest (~80% volume) of Geosphere. About 2900 km thick.

3. Core: Innermost, most dense and hot. Consists of Iron and Nickel. Outer core is liquid or molten Ni-Fe and inner core is solid Ni-Fe. About 3500 km.


Hydrosphere: consists of all Earth’s water.
Oceans ~97.5%
Glaciers ~ 1.8%
Ground water ~0.63%
Atmosphere ~ 0.001%
Streams and lakes ~ 0.01%
~12 km deep maximum.

Atmosphere: Mixture of gases (99% of atmosphere is within about 30 km high)
Nitrogen ~78%
Oxygen ~21%
Inert gases ~1%
CO2 ~ 0.03%; methane, Hydrogen, etc. are very small amount. This atmosphere supports life on our planet and shields it from high radiational heating and cooling. Circulation of atmosphere maintains temperature.


Biosphere: ~15 km. Includes the hydrosphere, upper geosphere and the lower atmosphere. Changing very rapidly with time (Fig. 1-6) that could threaten the environment.


Geologic Time: Age of Earth ~4.6 billion years. In the primordial stage, there was no crust, no ocean, no living organisms, and the atmosphere was mainly composed of hydrogen and helium (light) gases. Life existed as early as ~3.8 billion years (single celled organisms). About 543 million years ago, more complex life forms evolved. Dinosaurs existed about 225 million years to almost 65 million years (MYR).

Homosapiens came about 4 million yrs ago (single stroke of a file on middle finger nail if the whole life of Earth is as long as your arm).

[Jessica]

GEOSPHERE

• Planets accreted from dust into planetesimals
• Planetesimals clumped together to form planets
• Colliding pieces (and radioactivity) created heat, warming the young Earth to melting
• This ended (or Earth started) about 4.6 billion years ago
• 3 major layers
  
  • Dense metallic core - Outer core liquid, inner core solid, 6000°C Ni-Fe
  • Less-dense rocky mantle - Changes with depth, some parts solid, others weak and plastic-like, flowing slowly
  • Even less dense surface crust - Crustal material varies widely

LITHOSPHERE