Approximately 3.7 million years ago, the largest marine predator that ever lived roamed the
oceans.
Known as the megalodon shark, individuals were truly massive with lengths exceeding
58 feet and weights exceeding 100,000 pounds.
These apex predators had unusually large sharp teeth 7 inches or 17.5 centimeters long, such
as this fossilized specimen I am holding.
However, within 100,000 years, this shark species would be extinct.
During the next 1 million years, a number of similar extinctions occurred among marine
megafauna, largely due to the slow decrease in temperature around the planet.
Then, 2.5 million years ago, 36% of marine megafauna, along with a number of species
on land suddenly went extinct.
The cause of this small scale mass extinction was the beginning of the planet's most recent
ice age, which was likely triggered by a large asteroid impact.
This asteroid impact occurred off the coast of Chile in the deep ocean, creating megatsunamis
which raced around the planet.
The deposits from these megatsunamis have been widely since found along the western
coast of South America.
So, how did a large asteroid impact trigger the planet's latest ice age along with a mass
extinction?
This video will answer this question and discuss the Eltanin impact crater.
The Eltanin impact crater is located far off the coast of southern Chile, where it is 1,370
kilometers west southwest of the city of Punta Arenas.
Although difficult to see due to the low resolution of ocean topography in the area, a 35 kilometer
wide circular depression can be spotted with a large central peak typical of complex impact
craters.
It originated approximately 2.51 million years ago, when the Earth was already experiencing
a long term cooling trend.
At the time, a 3 kilometer or 1.9 mile wide asteroid was on a collision course with Earth.
This asteroid had an unusual composition, containing large brecciated fragments with
equal parts metallic nickel iron and silicate minerals.
Known as a mesosiderite, it originated due to an ancient massive collision of the asteroid
belt asteroid Vesta, when a large impacting body ejected material ranging from the crust
to its core.
These pieces later resolidified together, forming a family of rare meteorites.
As the asteroid entered the upper atmosphere, it was travelling at a speed of 20 kilometers
per second or 45,000 miles per hour.
Animals who lived on the planet at the time including llamas may have looked upwards and
seen a bright streak of light travel across the sky.
Moments later, an explosion equivalent in energy to the detonation of 3 million megatons
of tnt occurred, as the asteroid struck a 4900 meter deep section of the ocean floor.
This powerful explosion pulverized a large section of water and crust over a vast area,
generating a magnitude 8.5 earthquake.
Simultaneously, a powerful shockwave was generated, causing limbs to rip off of trees at 1400
kilometers distant on the western coast of Chile.
Due to the vast amount of water which was ejected high into the air, a temporary 1 kilometer
tall tsunami near the impact site was generated.
This tsunami wave would dissipate over time, but would cause 200 meter high waves to strike
the western and southern coasts of South America alongside the Antarctic Peninsula. 8 hours
later, a 60 meter high wave reached the eastern coast of New Zealand.
After another 2 hours, 35 meter high waves reached the southern coast of Mexico and Australia.
While the impact of the tsunami was extreme, it was not the direct cause of the subsequent
mass extinction.
Rather, the impact caused a temporary impact winter as large volumes of dust and rock were
thrown high into the air, causing a severely decreased amount of sunlight to reach the
ground.
During this brief period, large ice caps and snowcover quickly expanded across extreme
northern and southern latitudes.
When the effects of the impact winter faded, the cooling remained as these glaciers now
reflected large amounts of sunlight into space.
This decreased Earth's average temperature, creating a feedback loop which triggered the
planet's most recent ice age.
Many species were unable to survive this sudden change, causing widespread extinctions.
Thanks for watching.
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