The Atlantic Coastal Plain of the United States stretches along the Atlantic coastline from
New York to Florida.
It consists of sandy beaches, marshlands, barrier islands and the continental shelf.
It is the flattest terrain of the United States, and this is where a multitude of Carolina
Bays are found.
The Atlantic Coastal Plain is made of gently sloping Mesozoic and Cenozoic sediments, with
the sedimentary wedge thickening toward the sea, reaching a maximum thickness of about
3 kilometers or 10,000 feet in the vicinity of Cape Hatteras, North Carolina.
The thick sediments allowed the creation of the Carolina Bays, and the porous level ground
has made it possible for the fragile sandy structures to resist thousands of years of
erosion.
How did the Atlantic Coastal Plain originate?
The Atlantic Coastal Plain is the result of millions of years of tectonic activity and
ocean development.
The internal structure of Earth, excluding the atmosphere and the oceans, consists of
an outer crust of silicate rocks, called the lithosphere, a highly viscous asthenosphere
and solid mantle, a liquid outer core whose flow generates the Earth's magnetic field,
and a solid inner core.
The thickness of the crust varies from about 30 kilometers to as deep as 100 kilometers.
The lithosphere consists of a number of large tectonic plates that have been slowly moving
since about 3.4 billion years ago.
Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras.
It was not the first supercontinent.
It assembled from earlier continental plates during the Carboniferous Period approximately
335 million years ago, and it began to break apart about 200 million years ago, at the
end of the Triassic and beginning of the Jurassic.
The proximity of all these land masses allowed the dinosaurs to migrate and populate most
of the world.
The concept that the continents once formed a contiguous land mass was proposed in 1912
by Alfred Wegener, the originator of the theory of continental drift.
Modern studies are still trying to work out the details of when and how Pangea broke up.
This paper published in 2009 uses the distributions of magnetic anomalies in North America and
in Africa to try to determine the congruence of the tectonic plates and their time of separation.
This image illustrates the tectonic plate reconstruction at the Triassic–Jurassic
boundary, 200 million years ago.
The oceanic crust associated with the magnetic anomalies is shown in yellow and the orange
lines identify the boundaries of rift zones.
Present-day coastlines are shown for reference, and North Carolina and Mauritania are labeled.
The east coast of the United States, from Maine to Florida, was adjacent to Morocco
and Mauritania in western Africa.
The volcanic eruption of the Central Atlantic Large Igneous Province caused a mass extinction
that killed 20% of all marine families.
This cataclysm marks the transition from the Triassic to the Jurassic Period.
The separation of the tectonic plates along this rift created the northern Atlantic Ocean
and started the development of the Atlantic Coastal Plain.
This colorized map of the supercontinent Pangea shows the contact of North and South Carolina
with Mauritania 200 million years ago.
As the seafloor expanded, the continents on opposite sides of the ridge moved away from
each other.
Today, the North American and Eurasian tectonic plates are separated by the Mid-Atlantic Ridge.
The two continents are moving away from each other at the rate of about 2.5 centimeters
or one inch per year.
The Atlantic Coastal Plain has a different coloration in satellite images from Google
Earth.
By drawing a line separating the pale green from the dark green portions of the image,
we can identify the boundary of the Atlantic Coastal plain.
The steep change from the Atlantic Coastal Plain to the higher and rougher landscape
can be seen in this transect of the terrain.
There is a change of 52 meters of elevation in a distance of 4 kilometers.
The flat terrain has many Carolina Bays, but there are very few on the rough elevated terrain.
Today, we are going to take a closer look at Bear Swamp Bay in South Carolina.
This LiDAR image shows Bear Swamp Bay nestled on a strip of land at the confluence of the
Great Pee Dee River and the Little Pee Dee River.
Today, the Great Pee Dee River is a meandering stream, but its flood plain has a width of
2.5 kilometers.
The Little Pee Dee River is also a small stream, but its flood plain has a width of 1.5 kilometers.
Bear Swamp Bay is 56 kilometers from the Atlantic Ocean and Myrtle Beach, South Carolina.
As we zoom in, we can see that there are not very many Carolina Bays on this terrain.
There are traces of some very large bays, but most small bays have disappeared due to
water erosion.
Bear Swamp Bay is at an elevation of 11 meters above sea level and there is a group of overlapping
Carolina Bays with well-defined rims to the southeast on terrain at 13 meters above sea
level.
The order in which these Carolina Bays were created can be deduced from the way in which
the bays overlap using the law of superposition.
The Glacier Ice Impact Hypothesis proposes that one or more extraterrestrial impacts
on the Laurentide Ice Sheet by the Great Lakes ejected pieces of ice in ballistic trajectories.
The secondary impacts produced seismic vibrations that liquefied unconsolidated soil, and the
oblique impacts of glacier ice created inclined conical cavities that became shallow elliptical
basins by viscous relaxation.
The east side of Bear Swamp Bay has evidence of splash zones.
These splash zones are characteristic of bays that were formed by impacts on rivers or lakes.
The splash zones generally have scalloped edges and are located by the east rim of the
bays due to the influence of strong westerly winds when the bays were formed.
The image on the right is Jones Lake Bay in North Carolina.
Bear Swamp Bay overlaps a small bay.
The ballistic sedimentation of the glacier ice boulders that formed the bays lasted from
6 to 9 minutes after the extraterrestrial impact on the Laurentide Ice Sheet by the
Great Lakes, so the impacts that came later overlaid the craters made by the earlier impacts.
The inset shows a series of experimental impacts forming conical penetration funnels.
After viscous relaxation, the conical cavities become elliptical basins and the flanges of
the impact cavities become the raised rims of the basins.
The satellite view of Bear Swamp Bay does not show its geological features as prominently
as the LiDAR image.
This bay is surrounded by roads.
Bear Pond road is to the northwest.
Goose Pond road follows the southwest contour of the bay, and Highway 9 runs along the northeast
of the bay.
Bear Swamp Bay is currently in use as a tree plantation.
There are several buildings to the west of the bay.
The bay does not appear to have any drainage ditches, but there is an easement that traverses
the southeast portion of the bay for high voltage lines.
A test for ellipticity helps to distinguish Carolina Bays from other types of geological
structures like the thermokarst lakes in Alaska.
This test involves plotting points along the perimeter of the Carolina Bay and running
a program to fit an ellipse to the points.
The book by Professor Jay Melosh titled "Planetary Surface Processes", published in 2011, acknowledges
the existence of the Carolina Bays, but dismisses them with a scornful remark.
The textbook says, QUOTE: "Thawed permafrost expels water and contracts, sagging downward
into small ponds that collect more water end enhance melting.
Such thaw lakes are common, creating landscapes packed with kilometer-diameter circular to
elliptical ponds that are often aligned with the prevailing wind.
Such lakes constitute the infamous Carolina Bays, which impact crater enthusiasts persistently
claim to be of impact origin in spite of the complete lack of evidence for impacts."
END QUOTE.
Ignoring the Carolina Bays in geology books is bad enough, but it is much worse to implant
in the minds of geology students that the Carolina Bays are "infamous" and that it is
ridiculous to even consider their impact origin lest you become one of those foolish impact-crater
enthusiasts.
This bias is widespread in the geological community and it is difficult to overcome
when a respected impact expert like Professor Melosh promotes it.
The Carolina Bays are indeed different from thermokarst lakes.
Carolina Bays have mathematically elliptical geometry with raised rims, and they are oriented
toward the Great Lakes.
Thermokarst lakes have circular to elongated shape; they form as sinkholes, and they are
oriented toward lower terrain.
This is why it is important to fit ellipses by the least squares method to distinguish
Carolina Bays from Alaska's thermokarst lakes.
The Carolina Bays and thermokarst lakes may appear similar, but if they are not elliptical
with raised rims and oriented toward the Great Lakes, they cannot be Carolina Bays.
The heading of Bear Swamp Bay is 139.27 degrees.
By extending this heading as a great circle trajectory toward the Great Lakes, we find
that it leads to the convergence point of many other Carolina Bays, just west of Lake
Michigan.
The South Chippewa Basin in Lake Michigan was speculated to be the site of one of several
extraterrestrial impacts in a book by Richard Firestone published in 2006.
Ellipses are conic sections, so it is not surprising that impacts that create inclined
conical cavities look elliptical when viewed from above.
The penetration funnels have flanges that become raised rims as can be demonstrated
by experimental impacts.
A paper published in 2012 by Ted Bunch and several co-authors has an illustration of
an Australasian tektite that shows the raised rims of an elliptical impact cavity and the
tiny spherule that made the impact at the apex of the crater.
The elliptical cavity is just a few micrometers in length, which is millions of times smaller
than Bear Swamp Bay.
The physical forces that make a crater are somewhat invariant of scale, but the main
difference is that target strength dominates the excavation of microcraters whereas gravity
plays the dominant role for large craters.
Bear Swamp Bay is located 1213 kilometers from Lake Michigan which is assumed to be
the point from which the ice boulder that made the basin was launched.
The basin has a width of 787 meters and a length of 1,153 meters.
The width-to-length ratio corresponds to an impact angle of 43.1 degrees.
The diameter of the glacier ice projectile that made the basin is estimated to be 231
meters, which is one fifth of the basin length.
Ballistic equations indicate that the glacier ice boulder that made Bear Swamp Bay was launched
at a speed of 3.453 kilometers per second.
It had a flight time of 8.02 minutes and reached a height of 284 kilometers above the surface
of the Earth.
The trajectory was a suborbital space flight in the vacuum of space.
The kinetic energy of the impact that made Bear Swamp Bay was equivalent to 8.4 megatons
of TNT, which would have caused seismic vibrations of magnitude 8.1.
The flat, porous terrain of the Atlantic Coastal Plain is one of the reasons why the Carolina
Bays have been well preserved on the East Coast.
By contrast, the Nebraska Rainwater Basins, which are in rougher terrain do not show the
same degree of preservation.
It boggles the mind to think that the eastern coastline of the United States was adjacent
to Mauritania in Africa 200 million years ago, when today these land masses are separated
by 6000 kilometers.
The resistance to the idea that continents move is one of the reasons why plate tectonics
was only accepted as a valid hypothesis in the middle of the twentieth century after
the discovery of the Mid-Atlantic Ridge.
Thank you for joining me in the investigation of the Carolina Bays and the Younger Dryas
cataclysm.
There is a link to the LiDAR visualization tool in the description of the video.
My book about the Carolina Bays is available at Amazon.
Please subscribe to my YouTube channel to be notified of future videos about the Carolina
Bays and other scientific topics.