The Earth Story

The Chesapeake Bay Crater

35 million years ago, the Earth was much warmer than today due to higher abundances of carbon dioxide in the atmosphere. There were either small or no ice caps at the poles, leading to high sea levels that flooded the edges of the continents that are exposed today. This was the situation when a large rock from space came hurtling in, hitting the submerged continental shelf off the coast of what is today the state of Virginia. The object was between 3 and 5 kilometers in diameter. The impact of this rock caused a massive explosion and formed a crater 85 kilometers in diameter. It shattered the existing rocks, creating a debris pile known as a breccia that has since been buried by sediment shed off the continent.

The Chesapeake Bay Impact Structure still controls features of the shoreline today. It’s no coincidence that it sits right at the mouth of the modern day Chesapeake Bay.

The presence of this crater has caused the land above to subside, or sink, more than the surrounding land for 35 million years. That subsidence has caused rivers to flow to this location, making it a central point for erosion and downcutting.

15,000 years ago, sea level was much lower due to the presence of huge ice caps, so rivers flowed through the Chesapeake Bay impact structure out to sea, cutting wide canyons. When sea level rose, it flooded those canyons, creating shoreline features called estuaries around the world. The Chesapeake Bay is an estuary created by the flooding of river valleys that were fixed in location by an asteroid impact 35 million years ago. The East Coast of the United States today is shaped, in part, by a rock from space that landed tens of millions of years ago.

-JBB

Image credits and more: http://pubs.usgs.gov/fs/fs49-98/ https://commons.wikimedia.org/wiki/File:Chesapeake_Crater_boundaries_map.png

Swimming Reptiles may be gone, but waters of their ocean remains!

Thirty-five million years ago, that’s the Eocene to you, an asteroid or comet hit the earth making a 137 km diameter hole which now makes up a lot of Chesapeake Bay. This in itself is an earth event of spectacular importance. Ejecta was sent everywhere, tsunamis pounded the Blue Ridge Mountains, extinction was rampant among marine creatures and land mammals. But…

While fracturing 11 km depth of bedrock, the impact event managed to seal off an old reservoir of sea water, preserving it much like an ancient bug in amber. Again, this is nice, but…

But… studies of the salty water found at a depth today of 1km by the USGS deduce that this water is actually REAL seawater of the Cretaceous!

These waters were held in sediments that collected in the ocean’s depths. The water is far saltier than today’s oceans, twice as salty. It’s ratio of chloride and bromide peg it as ocean water. Ocean water accrues helium with age, and the amount of helium found within these waters requires 100 to 150 million years to accumulate…

Which places us back into the Cretaceous. When the Atlantic was young, when reptiles were swimming monsters and dinosaurs testing the waters along the beach at its edge with their toes, these waters made up the ancient oceans of the earth.

Annie R Image is a Free Wallpaper of a National Geographic image (2005): http://wakpaper.com/id3553/dinosaurs-wallpaper-039-free-wallpapers-desktop-hd-1024x768-pixel.html

More references: http://www.nature.com/nature/journal/v503/n7475/full/nature12714.html http://earthsky.org/science-wire/earths-oldest-large-body-of-seawater-identified-under-chesapeake-bay?utm_source=EarthSky+News&utm_campaign=6ce90d32a5-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-6ce90d32a5-393730545 http://www.redorbit.com/news/science/1113011029/impact-crater-oldest-seawater-chesapeake-bay-112213/ http://news.nationalgeographic.com/news/2001/11/1113_chesapeakcrater.html

The Chesapeake Bay Crater 35 million years ago, the Earth was much warmer than today due to higher abundances of carbon dioxide in the atmosphere. There were either small or no ice caps at the poles, leading to high sea levels that flooded the edges of the continents that are exposed today. This was the situation when a large rock from space came hurtling in, hitting the submerged continental shelf off the coast of what is today the state of Virginia. The object was between 3 and 5 kilometers in diameter. The impact of this rock caused a massive explosion and formed a crater 85 kilometers in diameter. It shattered the existing rocks, creating a debris pile known as a breccia that has since been buried by sediment shed off the continent. The Chesapeake Bay Impact Structure still controls features of the shoreline today. It’s no coincidence that it sits right at the mouth of the modern day Chesapeake Bay.  The presence of this crater has caused the land above to subside, or sink, more than the surrounding land for 35 million years. That subsidence has caused rivers to flow to this location, making it a central point for erosion and downcutting. 15,000 years ago, sea level was much lower due to the presence of huge ice caps, so rivers flowed through the Chesapeake Bay impact structure out to sea, cutting wide canyons. When sea level rose, it flooded those canyons, creating shoreline features called estuaries around the world. The Chesapeake Bay is an estuary created by the flooding of river valleys that were fixed in location by an asteroid impact 35 million years ago. The East Coast of the United States today is shaped, in part, by a rock from space that landed tens of millions of years ago. -JBB Image credits and more: http://pubs.usgs.gov/fs/fs49-98/ http://commons.wikimedia.org/wiki/File:Chesapeake_Crater_boundaries_map.png