Today’s Image of the Day from NASA Earth Observatory features a collection of Carolina bays near Bladen Lakes State Forest in North Carolina.
According to Christopher Swezey of the U.S. Geological Survey, most Carolina bays likely formed episodically during the last glacial maximum and the beginning stages of deglaciation, a period that spanned 40,000 to 11,000 years ago.
Many of the bays have elliptical shapes oriented in a southeast-northwest direction. This orientation is a product of the prevailing winds when the lakes were forming, explained Swezey.
“The dominant wind direction in this part of North Carolina was from the west, and that wind set up gyres in the lakes that eroded shorelines on the northwest and southeast margins of the lake.”
One study estimated that there are up to 500,000 Carolina bays in the Atlantic coastal plain.
“We now know that was a really conservative estimate,” said Swezey.“With the availability of modern LIDAR data, we are seeing many more of them than were previously recognized.”
The way the bays are distributed indicates that permafrost extended for several hundred kilometers south of the ice sheet.
“This is noteworthy because many geologists who studied glaciation in the past have suggested that frozen ground extended only as far south as northern Virginia during the last ice age,” said Swezey.
Image Credit: NASA Earth Observatory