Part II: Solar System The Earth Part 2 Updated: Apr 9, 2013

2 C. Above the Earth The Magnetosphere The Atmosphere Ecology, Life

Earth’s Magnetic Field 3 Earth’s Magnetic Field The magnetic axis is slightly tilted with respect to the rotational axis of the Earth. The angle slowly changes. Note: this slide has the magnetic field arrows going in the wrong direction! The North pole of the earth is a South magnetic pole!

4 Earth’s magnetic field traps particles ejected from the Sun (the solar wind)

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Remember the magnetic field and the aurora 6 Remember the magnetic field and the aurora Atomic particles (electrons, protons, etc.) ejected in all directions from the Sun form a solar wind that is intercepted by the planets. The magnetic fields of the planets trap and divert the solar wind, and cause aurorae.

The solar wind particles are trapped in a very large-scale 7 The solar wind particles are trapped in a very large-scale structure surrounding the Earth. This structure is called the magnetosphere, and it contains, among other things, the Van Allen Belts that were discovered from some of the earliest satellites that the U.S. put into space, in the late 1950s. The magnetosphere extends a distance equal to about 10 times the radius of the Earth in the direction toward the Sun, and much farther in the direction opposite the Sun.

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2. What is the atmosphere made of ? 12 2. What is the atmosphere made of ? Nitrogen 78% Oxygen 21% “Other”, making up 1% Argon Water Vapor (H2O) Carbon Dioxide (CO2) Methane (CH4)

13 Compare to Venus & Mars

What are Molecules? Molecules are combinations of atoms 14 What are Molecules? Molecules are combinations of atoms A molecule has chemical properties that are different from the individual atoms that compose it Example: Ordinary salt is sodium + chlorine (Na + Cl = NaCl). Salt is very different from either of its component atoms taken alone.

The components of the lower atmosphere (where we live) 15 The components of the lower atmosphere (where we live) Nitrogen (N), found in pairs that make molecules (N2) Oxygen (O), also found in pairs (O2) Carbon dioxide (CO2) Water vapor (H2O) Argon (Ar) Many other molecules in trace (very tiny) amounts

Basic Structure of the Earth’s Atmosphere 16 Basic Structure of the Earth’s Atmosphere

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22 3. Life, Global Warming

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Forces that Shape the Face of the Earth 32 Forces that Shape the Face of the Earth Impacts Big ones are rare, small ones more frequent Crater-forming impacts every 1000 years Major disaster every 50-100 million years

33 Figure 7.16 Aftermath of the Tunguska Explosion This photograph, taken 21 years after the blast, shows a part of the forest that was devastated by the 15-megaton explosion as a stony projectile about the size of a large office building (60-m diameter) collided with our planet. (Novosty) Fig 7-16, p.167

Meteor impact crater in Arizona, age 50,000 years, 34 Figure 7.17 Meteor Crater in Arizona Here we see a 50,000-year-old impact scar, made by the collision of a 50-meter lump of iron with our planet. While impact craters are common on less-active bodies such as the Moon, this is one of the very few well-preserved craters on the Earth. (Meteor Crater, Northern Arizona) Meteor impact crater in Arizona, age 50,000 years, diameter of crater ~1 mile. Fig 7-17, p.168

35 Figure 7.18 A 20-km Asteroid Hits the Earth This painting shows an impact similar to the one that led to a mass extinction 65 million years ago. (Painting by Don Davis) Fig 7-18, p.168

Forces that Shape the Face of the Earth 36 Forces that Shape the Face of the Earth Erosion 10% of Earth’s surface is covered by glacial ice (but is rapidly decreasing!) Ice at the South Pole moves 10 meters per year Ice and water remove large amounts of land Wind erosion removes layers of rock and soil Erosion has “erased” entire mountain chains, thousands of impact craters, filled ocean basins, and generally altered the entire surface of Earth

37 Erosion by Glaciers Glacier near Bern, Switzerland

38 Erosion by Floods

The History of the Earth 39 The History of the Earth

Conclusion: Earth is a Dynamic Planet 40 Conclusion: Earth is a Dynamic Planet

Notes Many slides have no caption and I don’t what they are!