GED Practice

GED Science Review: The Changing Earth

Directions: Choose or write the answer to each question.

Earth's crust is divided into large sections called plates. Earthquakes occur where the edges of two pates move past each other, or where one plate is pushed into or under the other. In some cases, mountain ranges form over millions of years at plate boundaries. For example, the Nazca plate pushing under the South American plate formed the Andes mountains. There are two main ways of predicting earthquakes. The first is to study the history of large earthquakes in an area. Based on past occurrences, scientist can determine the probability of another earthquake happening. The second method relies on measurements of seismic waves and movement along faults. Scientist measure wave activity using seismic instruments. They also use Global Positioning System (GPS) receivers installed along the San Andreas fault in California and faults in Turkey and Japan. Using signals from GPS satellites, the receivers give precise location data. Thus scientists can now monitor how much movement occurs along a fault. Using this type of information as well as historical data, they can calculate the probability of an earthquake occurring. Earthquakes tend to occur in clusters that strike a single area in a limited time. There are foreshocks, which occur before the large mainshock. Then there are aftershocks. So far, scientists are better at predicting aftershocks than foreshocks or mainshocks. Still, earthquake predictions in California have helped. For example, in June 1988, the San Francisco area experienced a foreshock measuring 5.1 on the Richter scale. Scientists predicted a mainshock would occur within five days. In response, local government emergency managers ran preparedness drills. Sixty-nine days later, the magnitude 7.1 Loma Prieta mainshock occurred. Local officials claim they were better able to respond than they would have been without the forecast. Still, there were 63 deaths and $6 billion in damage.

  1. Based on the passage, which of the following is a cause-and-effect relationship?
    • Earthquakes created the South American plate.
    • Mountains cause plates of Earth's crust to collide.
    • Earthquakes are caused by movements of Earth's crust.
    • Division of Earth's crust into plates is the result of earthquakes.
  2. Which of the following practices improved scientists' predictions of the likelihood and strength of future earthquakes?
    • analyzing the formation of geographical features in an area
    • measuring the strength of earthquakes using the Ritcher scale
    • analyzing historical data and measuring seismic activity along faults
    • measuring the motion of plates through the use of signals from GPS satellites
  3. The U.S. government funds much earthquake research. Based on information from the passage, what is the main reason the government provides this funding?
    • to reduce our reliance on the Richter scale
    • to learn more about the formation of the Andes mountains
    • to reduce loss of life and property damage from future earthquakes
    • to improve seismic instruments so they can be replaced with GPS satellites

      Questions 4 and 5 refer to the following passage.

      Earthquakes and volcanoes can quickly change the landscape, but weathering usually produces gradual changes. Weathering is the process by which rocks are broken down as a result of exposure to sun, wind, rain, ice, and other factors in the environment.
      There are two main types of weathering: mechanical and chemical. In mechanical weathering, rock breaks into bits but its composition remains the same. For example, when water freezes in the cracks of rock, it expands, widening the cracks. Eventually, this freeze-thaw weathering can crumble the rock. However, this crumbled rock is the same as the original rock. Chemical weathering occurs when substances, such as carbonic acid in rainwater, combine with the rock, dissolving certain minerals and changing the rock's chemical makeup. Living organisms can cause both mechanical and chemical weathering. Roots from plants can grow into the cracks in a rock, making the cracks bigger. Lichens can grow on a rock, producing chemicals that break down the hard material.
  4. Determine the type of weathering represented by each of the following examples. write C for chemical and M for mechanical.
    • Groundwater dissolves limestone.
    • Ice breaks granite into pieces.
    • Expanding roots widen a crack in a rock.
    • Acid rain wears away a portion of marble.
  5. when iron-containing rock reacts with oxygen, the iron is converted to iron oxides, which weaken the rock's structure. In a paragraph, identify your answer by citing evidence from the passage.


  1. Earthquakes are caused by movements of Earth's crust.
  2. measuring the motion of plates through the use of signals from GPS satellites
  3. to reduce loss of life and property damage from future earthquakes
  4. chemical; mechanical; mechanical; chemical


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