The goal of this lab is to examine how sea level rise and fall in the recent geologic past has changed the location of the coastline in eastern North Carolina. During the Pleistocene (the last 2.5 million years), the Earth’s climate has been dominated by the presence of large continental ice sheets in both the northern and southern hemisphere (the Arctic and Antarctic). This climate overall has been termed an Ice House climate. This is in contrast to a Hot House climate that contains no continental ice sheets. However, within this time period the size and number of the continental glaciers has varied on approximately a 100,000 year time frame due to orbital variations called Milankovitch cycles. Milankovitch cycles influence the amount of sunlight the Earth receives and have caused ice sheets to grow and shrink according to our best scientific interpretations. As ice sheets grow and melt they have caused sea level to also move up and down. The goal of this lab is to identify the location of past shorelines in eastern North Carolina and offshore and corelate them with specific glacial events.
Guiding questions: What happens to sea level when glaciers expand and what happens to sea level when they shrink and melt away? In particular, 1) Where was the coastline during the Last Glacial Maximum (22,000 years ago) and 2) Where was the coastline 120,000 years ago during the last interglacial period?
You will use Google Earth to look for topographic features that indicate where these past coastlines might be located. The past coastlines can be observed in Google Earth, however these are somewhat tricky to pick out if you don’t know what you are looking for. So to help quantity this you will make two topographic profiles. Both will start at Cape Hatteras in the Outer banks (the current coastline). One will extend to the west (A-A’) and the other will extend to the east (B-B’). Use what we know about past sea level rise and fall and look for topographic “steps” in the landscape that are past wave cut terraces and beach ridges indicative of past shorelines.
Make a hypothesis about where the coastline was at 22,000 years ago and at 120,000 years ago and discuss this with other students in your group.
22,000 years ago, the coastline was further into the sea because at that time, the continental ice sheet was at its all-time high. There was a lot of water frozen as ice in the Northern and Southern Hemisphere. 120,000 years ago, the glacial environment in the hemispheres has melted and released most of the water in the ocean. Therefore, the sea levels had significantly risen causing