Thursday, March 8, 2007

Earth - Our Home Planet

By Princessa

Earth - Our Home Planet

Apollo 17 astronauts captured this snapshot of the Earth System on their way to the Moon in 1972. Essentially everything that was a part of the System then is still a part of the System today-that's why it's considered a closed System. All of the matter (solid, liquid, and gas) and all of the processes that move energy and materials from one part of the planet to another make up the Earth System.

Four major parts of Earth work together as a complex system: rocks, water, air and life. On a global scale, each part can be thought of as a sphere, roughly the same size and shape as the planet. The four parts are called the geosphere (earth), hydrosphere (water), atmosphere (air), and biosphere (life).

The surface of the geosphere, where the rocky part of our planet is in contact with water, air, and/or life is generally where the spheres intersect and affect each other. The processes that move matter and energy from one sphere to another are called sphere interactions.

Plants (biosphere) draw water (hydrosphere) and nutrients from the soil (geosphere) and release water vapor into the atmosphere. Humans (biosphere) use farm machinery (manufactured from geosphere materials) to plow the fields, and the atmosphere brings precipitation (hydrosphere) to water the plants. Energy from the sun is stored by plants (biosphere). When humans or animals (biosphere) eat the plants, they acquire the energy originally captured by the plants. Humans expend some of this energy arranging bricks and wood (geosphere and biosphere) into buildings.

Although it makes a fascinating stroy, it is not possible to journey to the center of Earth. Instead, scientists gather observations at the surface to construct models of Earth's internal structure. They analyze seimic data-information from earthquakes-to infer processes that occur inside the planet.

When an earthquake occurs, seismic waves travel through the planet. Every earthquake generates two types of waves-Primary (P waves), and Secondary (S Waves). A worldwide network of seismometers, instruments that track earthquakes, records the arrival of P and S waves from all over the globe. Observations and analysis of the waves have led geologists to infert he internal structure of Earth.

You just observed that P and S wave behavior is different in solids and liquids. P waves travel through both solids and liquids. S waves travel through solid material, but they cannot travel through liquids. This difference can be used to tell which parts of Earth's interior are solid and liquid.

Another difference in P and S waves is their speed. You saw that P waves travel faster faster than S waves. Also, P waves travel faster through solids than through liquids.

On March 1, 1872, Congress designated Yellowstone National Park as the first National Park. Today, Yellowstone is still one of the most frewuently visited national parks in the country.

When a place is designated as a national park, monument, or preserve, laws protect the land from being mined, commercially developed, or owned. These protected lands are set aside by the government to preserve natural, cultural, and historic resources for the enjoyment of current and future generations.

How we protect and manage natural resources often depends on what type of resource they are. Natural resources may be either renewable or nonrenewable. Renewable resources are those that are replaced in nature at a rate close to their rate of use. Nonrenewable resources exist in fixed amounts or are used up faster than they can be replaced in nature.

A variety of agencies help manage and protect natural resources in the United States. Some organizations, like the Forest Service and the Fish and Wildlife Service, focus on renewable resources.
The Bureau of Land Management (BLM) oversees many of the protected lands that are considered to be nonrenewable resources. BLM lands are managed in a way that enables usage while minimizing environmental damage.

Features or events on Earth's surface provide clues about what happens inside the planet. For instance, lava erupted from volcanoes on Earth's surface indicates that our planet has an internal temperature high enough to melt rock.

In this investigation, you'll explore patterns formed by geologic features at Earth's surface. You'll analyze patterns showing where lava erupts, earthquakes occur, and mountains form. From these patterns, you'll infer properties of Earth's crust—the solid, outermost portion of the geosphere.

Volcanoes reveal locations where Earth's internal heat escapes to the surface of the planet. Volcanic eruptions, lava flows, and hydrothermal activity such as geysers are all evidence of Earth's internal heat being released. Regions without volcanic activity keep heat inside the planet.

What do you notice about the pattern formed by volcanoes? Are they spread randomly across the globe or do they occur more in some areas than others? Why do some areas show a long line of volcanoes?

Earthquakes occur where solid rocks move against other solid rocks. Energy released during earthquakes is generated when rocks break. Locationd of earthquakes, therefore, provide information on where Earth's crust breaks in response to pressure.

The formation of folded mountains on Earth's surface can be compared to the process of wrinkling a flexible rug on a floor. As horizontal pressure is applied along the edge of a rug, folds appear perpendicular to the direction of pressure. On Earth, as horizontal pressure is applied to rocks, ridges and valleys form perpendicular to the direction of the pressure.

Now think about what each of the three features you've examined indicates about Earth's crust. Consider what Earth’s crust is like in areas where all three of these features occur together. How are areas where these features occur different from areas without volcanoes, earthquakes and mountain belts? Examine the patterns on the map and visualize a mental model of Earth's crust.

No comments: