Untitled Quiz

Solar System and the Earth

• The solar system consists of a medium-size star (the Sun) and eight planets orbiting it.
• Planets are of two types: inner planets (terrestrial planets) and outer planets (Jovian planets).

Inner Planets (Terrestrial Planets)

• Rocky planets near the sun
• Include Mercury, Venus, Earth, and Mars
• Small, high density, rocky
• Poor in ices and H/He
• Lack rings

Outer Planets (Jovian Planets)

• Giant gaseous planets
• Include Jupiter, Saturn, Uranus, and Neptune
• Large, low density, gaseous (H, He, CH4)
• Rotate rapidly
• Have rings and many moons
• Pluto is a small icy minor planet

Differences Between Inner and Outer Planets

• Density: Inner planets have densities of 3 g/cm³ or more; outer planets have densities of 1.6 g/cm³ or less.

Age of the Earth

• The Earth is estimated to be 4.5 to 4.6 billion years old.
• This is determined by radiometric dating, using an instrument called a mass spectrometer (Uranium, Thorium).
• The oldest rocks on Earth are found in the Canadian Shield (NW Territories near Great Slave Lake), dated at 3.96 billion years old. Prior to this, the oldest rocks were from the Isukasia region of Greenland, dating to 3.8 billion years.

Spheres of the Earth

• Earth consists of four spheres: atmosphere, hydrosphere, biosphere, and lithosphere.

Lithosphere

• The Earth's crust composed of igneous, sedimentary, and metamorphic rocks.

Hydrosphere

• The total mass of water on or near the Earth's surface.
• Covers 71% of Earth's surface.
• ~98% is in oceans
• 2% is in glaciers, groundwater, lakes, and streams (fresh water)

Biosphere

• Includes all life on Earth (plant and animal), in the sea and on land.

Atmosphere

• Consists of 78% nitrogen and 21% oxygen.
• Contains minor amounts of carbon dioxide, argon, and water vapor.
• Divided into layers, including troposphere (weather), stratosphere (ozone layer), mesosphere, thermosphere, and exosphere (outer space).

How do we know about the Earth's Interior?

• Drilling: Wells are mostly in the upper 7 km of the crust; the deepest (Soviet, Russian) well in the Kola Peninsula reached 12 km but stopped in 1989. Costs were over $100 million. Bottom hole temperature was 190°C.
• Volcanic activity: Materials brought up from below (Xenoliths = foreign rock from the mantle found in lava). Only useful to depths of about 200 km.
• Samples of the solar system (meteorites): Study of composition.
• Seismic waves: Study of waves generated by earthquakes and explosions. Seismic wave speed increases with depth (pressure, and density increase downward).

Earth's Internal Structure

• Earth has a layered structure defined by composition (crust, mantle, core) and physical properties (lithosphere, asthenosphere, mesosphere, outer core, inner core).

Crust

• Continental crust: Thick (up to 75 km), lower density (2.7 g/cm³), strongly deformed, and very old (billions of years).
• Oceanic crust: Thinner (about 8 km), higher density (3.0 g/cm³), comparatively undeformed, and much younger (< 200 million years).

Asthenosphere

• Part of the mantle that flows.

Physical Layers

• Lithosphere: Crust + upper portion of the mantle (solid & rigid), thickness varies from 10 km under oceans to 300 km under continents.
• Mantle: Middle layer, rich in minerals containing iron, magnesium, silicon, and oxygen. At over 1000°C, it is solid but can deform slowly in a plastic manner.
• Core: Composed of iron and nickel; remains extremely hot even after billions of years of cooling. Divided into a solid inner core and a liquid outer core. Inner core is solid due to extreme pressure.

Compositional Layers - Summary

• Crust: outermost layer; definite change at the base, two types (continental and oceanic)
• Mantle: Middle layer
• Core: Innermost layer