Age variation, by color, of the ocean floor

Solar winds stream toward the planet at over 400 km/s, and are deflected by the magnetosphere. Layers of Earth's atmosphere have temperatures so extreme that meteors are incinerated many miles above this spinning orb. Closer to Earth, rivers of air called jet streams race through the stratosphere. Weather processes at the surface regularly produce hurricanes, tornadoes, and cyclonic storms. And in the world ocean, tides, waves, and currents churn the seas.

Nor is Earth itself at rest. What we call solid earth is really large slabs of crust that float atop molten rock. Where slabs meet, earthquakes shake, mountain ranges rise, and volcanoes explode. Earth's landscape is under constant attack from the internal forces that drive these dramatic events, but the assault is even greater from another front — time.

Over 4.5 billion years of geologic history, time has transformed the Earth profoundly. Continents have drifted across the globe, a process you can witness first-hand on focus page 2a: Alfred Wegener and Continental Drift. Rivers have carved valleys and canyons, including the Grand Canyon, where layers of rock preserve a record of millions of years of Earth and life history. See it for yourself in our interactive tableau of the Grand Canyon on focus page 10c: History in Rock and Fossils. Then, try your hand at keeping 4.5 billion years of history in the right order on focus page 10e: Middle to Recent History.

NASA images Earth in a variety of ways in order to learn about its processes.

Still other rivers, rivers of ice called glaciers, have sculpted the landscape through the repeated advances and retreats of ice during Earth's many ice ages. Examine the coulees, fjords, and other characteristic formations they left behind on focus page 9b: Glaciers. Compare these with images of how coastal processes such as waves and currents carve the Earth's coastlines on 9e: Coastal Processes.

Even rocks are not rock solid. Once born from Earth's fiery interior, they are under constant attack at the surface. See how forces of erosion and deposition transform rocks in unit 7: The Rock Cycle, then see if you can identify which is which on focus 7c: Metamorphic rock. Better bone up - it's "hard."

Time Marches On

The Kuwaiti oil well fires during the Gulf War sent massive black clouds into the atmosphere.

What will be the legacy of humanity's time on Earth? Much progress has been made in predicting natural phenomena such as earthquakes and volcanic eruptions, but in other arenas, "progress" has a less hopeful meaning. Deforestation, acid rain, global warming, and strip mining disrupt natural processes beyond Earth's ability to recycle itself.

Can we learn to be at peace with this restless Earth before time runs out?

1. Earth's Structure
   1. Formation of the Earth
   2. The Core
   3. The Mantle
   4. The Crust
2. Plate Tectonics
   1. Alfred Wegener and Continental Drift
   2. Earth's History: Pangaea to the Present
   3. Plate Boundaries
   4. Mountains
3. Earthquakes
   1. What Makes a Quake
   2. The Four Faults
   3. Seismic Measurement
   4. Earthquake Effects
   5. Tsunamis
   6. Can Earthquakes Be Predicted?
4. Volcanoes: Part 1
   1. Volcanic Model
   2. Types of Volcanoes
   3. Volcanic Eruptions
   4. Volcanic Hazards
   5. Case Study: Mount Saint Helens
5. Volcanoes: Part 2
   1. Subduction Zone
   2. Rift Volcanoes
   3. Hot Spots
   4. Geothermal Features
   5. Volcano: Friend or Foe?
   6. Case Study: Hawaiian Islands
6. Minerals
   1. What Is a Mineral?
   2. Identifying Minerals by Physical Properties
   3. Rock-Forming Minerals
   4. Gems and Precious Metals
   5. Mineral Uses
7. The Rock Cycle
   1. Igneous Rocks: Forged by Fire
   2. Sedimentary Rocks: Layered Storytellers
   3. Metamorphism: Changed Rocks
8. Weathering and Soils
   1. Weathering Processes
   2. Soil Formation and Composition
   3. Soil Characteristics
   4. Humans and Soil
9. Surface Processes
   1. Mass Wasting
   2. Glaciers
   3. Rivers
   4. Karst Topography
   5. Coastal Processes: Down by the Sea
   6. Winds and Deserts
10. Geologic History
    1. Geologic Time Scale
    2. Fossils
    3. History in Rock and Fossils
    4. Early Earth History
    5. Middle to Recent History
11. The Living Earth
    1. The Nitrogen Cycle
    2. The Carbon Cycle
    3. The Oxygen Cycle
    4. Other Biotic Minerals
12. Our Role in Earth's Future
    1. Balancing the Spheres
    2. Natural Resources: Use and Re-Use
    3. Pollution
    4. Pollution Solutions