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How does a living thing become a fossil?

Teaching and Learning Focus

In the previous investigation, students discovered that living things can die and decay. Soft parts are more likely to decay than hard parts. For this reason, the most common fossils are bones, teeth, shells, and the woody stems of plants. For a fossil to form, an organism must be buried quickly so that any oxygen is cut off and its decay slows down or stops.

Why do some things become fossils, but others do not?

Teaching and Learning Focus

It is very likely that any organism on Earth will be either eaten by scavengers or decomposed by microorganisms after it dies. Organisms decompose more quickly when they are in contact with oxygen. Most environments exposed to the open air are in contact with plenty of oxygen, so the soft tissues of dead organisms, whether plants or animals, decay quickly. Many, if not most, underwater environments also have a lot of oxygen, since water can dissolve oxygen from the atmosphere.

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Why do hurricanes regularly hit Florida? How do earthquakes happen? What types of rocks are found in your backyard? Here you'll find answers to many of your questions about Earth science!

You can "dig deeper" into the science topics below. Explore curricula and instruction resources, teaching media resources, and outreach activities related to each topic. While this content is written for you, the teacher, you might find that you can adapt it for upper elementary students.

What is the difference between evaporation and condensation?

Liquid water consists of water molecules that are held near each other by attractive forces but are still free to move around among one another. Also, water molecules have thermal energy, in the form of extremely fast vibrations. Water molecules at a water surface occasionally vibrate so strongly that they fly out into the air to become vapor. At the same time, water molecules in the air occasionally crash back onto the water surface to join the liquid water. These motions are occurring all the time at the water surface.

What is the water cycle?

A "closed system" consists of a container that allows energy, but not matter, to pass back and forth across the walls of the container. The Earth's atmosphere, oceans, and land surface act as an almost closed system. Water moves along a variety of pathways in this closed system. This system of movement is called the "water cycle."

How do scientists use radar and satellites to observe and predict weather?

Radar (radio detection and ranging) has become an important tool for observing and predicting the weather. Radar was invented and developed in Britain and the U.S. at the beginning of the Second World War. It was used to detect the approach of enemy airplanes. An antenna sends out radio waves. The waves are reflected from solids or liquids in the air and received back by the antenna. The radar equipment shows the position and distance of the objects. The results are shown on a screen. The screen is similar to the screen of a television or a computer monitor.

What is the weather like at high altitudes?

You experience weather at the Earth's surface, but there is weather high in the atmosphere, too. Have you ever taken a ride in a hot-air balloon or climbed a high mountain? You would know that the air temperature usually decreases with altitude. The basic reason has to do with where the atmosphere receives its heat and where it loses its heat. The Earth's surface is heated by the sun at some times and places. It loses heat to outer space at other times and places. On balance, however, the Earth's surface gains more heat than it loses.

What is the difference between a cold front and a warm front?

Large masses of air, as much as a thousand miles across, take on certain weather characteristics when they stay at high latitudes (near the poles) or at low latitudes (near the equator) for several days at a time. They may be very cold or very warm, or they may be very humid or very dry. Then, as they move into other areas, they can affect the weather there very strongly.


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