Background: The southeastern elbow of the Cape Cod National Seashore is a fantastic example of beach evolution The region shown in this Google Earth file, near Chatham, shows a barrier Island and spit system that changes constantly. Normal tides and wave action move sediment around on a continuous basis, and storm systems can drastically alter their shape. Satellites have tracked this region for three decades, and using Google Earth, we can go back in time and see these changes.
Getting Started:
Download the Cape Cod. kml file (provided by NASA Earth Observatory) and open it in Google Earth Pro.
Make sure the Cape Cod file is checked in your Temporary Places and that everything else is turned off. If it did not automatically zoom you into Cape Cod when you opened the file, double click on the file name.
In the upper left corner of your map, there is a timeline bar with a date showing. You can drag the arrow back and forth across the timeline to show images from different dates.
Activity:
Slowly drag the arrow from the left to the right, going month to month through time, watching the barrier Island system. Stop when you see the first major change occur.
Very slowly drag the arrow back and forth until you figure out the time range when that major change occurred (you should be able to get it down to a specific two-month range within one year, for example, May-June 2013).
• What kind of event could have caused this big of a change?
Move the arrow ahead to 12/1989 and look at the configuration of the barrier Islands and spits. Now move it one click forward and look at the configuration at 1/1990.
• What happened in the middle of the upper barrier island? Where did the sediment move to?
Move the arrow ahead to 10/1992 and look at the configuration in comparison to 1/1993. At this point, the middle barrier Island became connected to the land, making it a spit.
Move the arrow to 11/1998 and compare it to both 12/1998 and 2/1999,
• What happened over this three-month period? What does this tell you about the energy and sediment supply in this region?
Move the arrow back to the far left, and quickly move the arrow to the right, going through the entire time scale.
• Which direction is the longshore current running in this area?
Look for the migration of sediment and structures in one direction, and make sure north is facing towards the top of the screen (if you click on the N on the compass, it will reorient the map so it is correctly aligned). Give your answer in a compass direction (e. g., northeast, south-southeast).
• Based on what you have seen in this timeline, when do the largest amounts of change occur in this area? is it during the summer or the winter? Why might that be?
• If a large hurricane was to come through this region, what might be the impact to the barrier island system? What about the mainland behind the barrier island?
• If you were in charge of this area, is there anything you would do to help protect both the people who live here and the natural environment?