# Earthquakes occur at faults.  Describe how the presence of a fault may result in an earthquake.

Lab with 15 easy questions-Lab 3 – Sea Ice, Plate Tectonics & Earthquakes

1. In the study of climate change, the concept of “anomalies” often comes up.  What is a temperature anomaly?  See figure 1-2 and p. 240 in your textbook (2)

A temperature anomaly refers to the difference between the average temperature in a given location for a specific period of time (usually 30 years) and the temperature for a particular day, week, or month. The temperature anomaly is typically expressed as a deviation from the long-term average, usually measured in degrees Celsius or Fahrenheit.

Temperature anomalies are used to track changes in temperature over time, particularly as they relate   to climate change. By comparing temperature anomalies over a period of years or decades, scientists can observe trends in temperature that can help them understand the impacts of climate change on the environment.

1. The National Snow & Ice Data Center monitors sea ice coverage and concentration.  The Sea Ice Index is calculated from this coverage to assess the change in sea ice compared with the 30-year average.

The “median ice edge” line on the map (pink line) represents the 30-year median ice extent.  How does the current sea ice extent compare to the 30-year median? (2)

If the current sea ice extent is below the 30-year median, it means that there is less sea ice now than there was on average during that 30-year period.

1. Examine the Monthly Sea Ice Extent Anomaly Graph (click on it to make it larger).  When was the last year that the sea ice extent anomaly (for the current month) was greater than the 1981-2010 mean sea ice extent? Hint: The 1981-2010 mean sea ice extent is the 0% value on the anomaly graph.(2)
2. Given the 1981-2010 mean sea ice extent labeled in the lower left-hand corner of the graph, calculate the current sea ice extent in millions of square kilometers. Show your work. Hint: Subtract the current sea ice extent anomaly, which you can read in the graph expressed as a percent, from the 1981-2010 mean.  You can check your answer against the “Total extent” value given on the Sea Ice Extent map.(3)
3. How does the trend in the extent anomaly graph compare with that of the temperature anomaly graph of Figure 4-34(Links to an external site.)Links to an external site. in your textbook?  What is the significance of this? (3)
4. What is the speed of Santa Cruz? (round your answer to the nearest hundredth) (2)
5. What is the speed of Santa Rosa? (round your answer to the nearest hundredth) (2)
6. Using page 128 (p.118 in 22nd edition) in your atlas, determine how many miles apart are Santa Cruz and Santa Rosa. Show your work (round your answer to the nearest whole number) (3)
7. You can calculate how fast the two cities are moving toward each other by adding up the absolute value of their speeds. Based on the distance that you calculated in the previous question, and the speed at which the two cities are moving toward each other, how many years will it take for Santa Cruz and Santa Rosa to “meet”? Remember that Speed = Distance/Time.  Note that 25.4 mm = 1 inch, 12 inches = 1 foot, 5280 feet = 1 mile, 1 mile = 1.61 kilometers (round your answer to the nearest whole number). Show your work. (3)

10.Using the Option settings (gear symbol on the upper right), switch to 30 Days, Significant Worldwide and zoom out to the World. Where did the two strongest of these earthquakes occur and what was their magnitude? (2)

1. Switch to 30 Days, Magnitude 4.5+ U.S.What can you say about the pattern of these significant earthquakes across the world? (2)
2. Zoom to California (click on the globe icon beneath the +/- zoom buttons). Switch to 7 Days, Magnitude 2.5+ U.S. Turn on the U.S. Faultslayer. What pattern do you notice in the distribution of earthquakes in the western U.S.? (2)
3. Where did the strongest of these earthquakes occurin the western U.S. and what was its magnitude? (2)
4. Go to the USGS “How Much Bigger…?” Calculator Links to an external site..  Enter the magnitude of the strongest earthquake you found in the previous question.  How much stronger (by energy released) was this earthquake than a 2.5 magnitude earthquake (one which is barely perceptible to humans). (2)
5. Earthquakes occur at faults.  Describe how the presence of a fault may result in an earthquake. See p. 436 and Figure 14-58 in your textbook. (2)
6. Zoom to North America (use the “Zoom to U.S.” option).  How many “Significant”earthquakes have occurred in North Americain the last 30 days (use the “30 days, Significant Worldwide” option)? Where have these earthquakes occurred? If near a plate boundary name the type of plate boundary (you should look this up). (3)
7. Switch to 7 Days, Magnitude 2.5+ U.S.Approximately how many 2.5+ magnitude earthquakes occurred away from plate boundaries (click on the “Only List Earthquakes Shown on Map” checkbox and pan/zoom around to get an approximate count)?  Where? (3) What are the best explanations for the occurrence of these specific earthquakes(you should look this up)? (bonus +1)