Universe Tenth Edition Chapter 9 The Living Earth Roger Freedman Robert Geller William Kaufmann III

9-1 What powers the motions of the Earth ’ s atmosphere, oceans, and land surfaces 9-2 How scientists have deduced the layered structure of our planet ’ s interior 9-3 The evidence that the continents are being continuously moved and reshaped 9-4 How life on Earth is protected from subatomic particles emitted by the Sun 9-5 How the evolution of life has transformed the Earth ’ s atmosphere 9-6 What causes the patterns of weather in our atmosphere 9-7 How human civilization is causing dramatic and adverse changes to our planetary habitat By reading this chapter, you will learn

9-1: Earth’s atmosphere, oceans and surface are extraordinarily active

Earth’s Dynamic Oceans

Earth’s Dynamic Atmosphere

Earth’s Dynamic Surface

Old and Young Rocks in the Grand Canyon

Convection in the Kitchen

The Greenhouse Effect

Chemical Differentiation and Earth’s Internal Structure

Seismic Waves

9-2: Studies of earthquakes reveals Earth’s layered interior structure

Earth’s Internal Structure and the Paths of Seismic Waves

Temperature and Melting Point of Rock Inside Earth

Fitting the Continents Together

The Breakup of the Supercontinent Pangaea

The Mid-Atlantic Ridge 9-3: Plate movement produces earthquakes, mountain ranges and volcanoes that shape Earth’s surface

The Mechanism of plate tectonics

The Separation of Two Plates

The Collision of Two Plates

Igneous, Sedimentary and Metamorphic Rocks

Earth’s Magnetosphere 9-3: Earth’s magnetic field produces a magnetosphere and reverses direction

The Aurora

Simulation of Earth’s Magnetic Dynamo

Magnetic Stripes on the Ocean Seafloor

The Increase in Atmospheric Oxygen 9-5: Earth’s atmosphere has changed substantially over our planet’s history

Temperature Profile of Earth’s Atmosphere 9-6: Like Earth’s interior, our atmosphere has a layered structure

Circulation Patterns in Earth’s Atmosphere

Earth’s Biosphere 9-7: A burgeoning human population is profoundly altering Earth’s biosphere.

Comparing Earth’s Atmosphere and Interior

The Human Population

The Deforestation of Amazonia

The Antarctic Ozone Hole

Atmospheric Carbon Dioxide is Increasing

Atmospheric CO 2 and Changes in Global Temperature

Global Warming

A Melting Antarctic Ice Shelf

Key Ideas The Earth ’ s Energy Sources: All activity in the Earth ’ s atmosphere, oceans, and surface is powered by three sources of energy. Solar energy is the energy source for the atmosphere. In the greenhouse effect, some of this energy is trapped by infrared absorbing gases in the atmosphere, raising the Earth ’ s surface temperature. Tidal forces from the Moon and Sun help to power the motion of the oceans. The internal heat of the Earth is the energy source for geologic activity.

Key Ideas The Earth ’ s Interior: Studies of seismic waves (vibrations produced by earthquakes) show that the Earth has a small, solid inner core surrounded by a liquid outer core. The outer core is surrounded by the dense mantle, which in turn is surrounded by the thin low-density crust. Seismologists deduce the Earth ’ s interior structure by studying how longitudinal P waves and transverse S waves travel through the Earth ’ s interior. The Earth ’ s inner and outer cores are composed of almost pure iron with some nickel mixed in. The mantle is composed of iron rich minerals. Both temperature and pressure steadily increase with depth inside the Earth.

Key Ideas Plate Tectonics: The Earth ’ s crust and a small part of its upper mantle form a rigid layer called the lithosphere. The lithosphere is divided into huge plates that move about over the plastic layer called the asthenosphere in the upper mantle. Plate tectonics, or movement of the plates, is driven by convection within the asthenosphere. Molten material wells up at oceanic rifts, producing seafloor spreading, and is returned to the asthenosphere in subduction zones. As one end of a plate is subducted back into the asthenosphere, it helps to pull the rest of the plate along.

Key Ideas Plate tectonics is responsible for most of the major features of the Earth ’ s surface, including mountain ranges, volcanoes, and the shapes of the continents and oceans. Plate tectonics is involved in the formation of the three major categories of rocks: igneous rocks (cooled from molten material), sedimentary rocks (formed by sediments in water), and metamorphic rocks (altered by extreme heat and pressure).

Key Ideas The Earth ’ s Magnetic Field and Magnetosphere: Electric currents in the liquid outer core generate a magnetic field. This magnetic field produces a magnetosphere that surrounds Earth. A bow-shaped shock wave, where the supersonic solar wind is abruptly slowed to subsonic speeds, marks the outer boundary of the magnetosphere. Most of the particles of the solar wind are deflected around the Earth by the magnetosphere. Some charged particles from the solar wind are trapped in two huge, doughnut- shaped rings called the Van Allen belts. An excess of these particles can initiate an auroral display. Earth’s magnetic field flips regularly, but with an average of about 300,000 years between reversals. These field flips are preserved in magnetizes rock on the ocean seafloor.

Key Ideas The Earth ’ s Atmosphere: The Earth ’ s atmosphere differs from those of the other terrestrial planets in its chemical composition, circulation pattern, and temperature profile. The Earth ’ s atmosphere evolved from being mostly water vapor to being rich in carbon dioxide. A strong greenhouse effect kept the Earth warm enough for water to remain liquid and to permit the evolution of life.

Key Ideas The appearance of photosynthetic living organisms led to our present atmospheric composition, about four-fifths nitrogen and one-fifth oxygen. The Earth ’ s atmosphere is divided into layers called the troposphere, stratosphere, mesosphere, and thermosphere. Ozone molecules in the stratosphere absorb ultraviolet light. Because of the Earth ’ s rapid rotation, the circulation in its atmosphere is complex, with three circulation cells in each hemisphere.

Key Ideas The Biosphere: Human activity is changing the Earth ’ s biosphere, on which all living organisms depend. Industrial chemicals released into the atmosphere have damaged the ozone layer in the stratosphere. Deforestation and the burning of fossil fuels are increasing the greenhouse effect in our atmosphere and causing a global warming of the planet.