Approximately 67 million years ago, the plant and animal life around Earth looked completely
alien.
Across much of the dense rainforests, towering bird like reptiles known as dinosaurs were
the dominant lifeforms around the planet, with the population in the tens of millions
across numerous species.
In the oceans, 2 meter wide floating rounded shells roamed the seas, where they were occasionally
hunted by 15 meter or 49 foot long reptilian predators called Mosasaurs, as shown by the
large bite mark in this ancient ammonite shell.
So, why are reptiles no longer the dominant lifeforms on the planet today?
The answer is one of the planet's deadliest mass extinction events which was caused by
the largest known impact event in the last 1 billion years of the planet.
For decades, it was suspected by some researchers that whatever caused the extinction of the
non avian dinosaurs was abrupt and deadly.
Around the planet, a definable layer which marked this extinction can be found which
is dated to 66 million years in age.
This layer contrasts with the surrounding rocks, and is defined by a horizontal stripe
of white kaolinite overlaid by dark black smectite and coal.
The presence of these clays indicated that abruptly something changed the dominant geology
of the planet.
A clue that this change was brought about by an asteroid impact came when unusually
high concentrations of the element iridium were detected in the aforemention rock layer,
which occurred at between 20 and 1,000 times higher concentrations than typical of rocks
in the Earth's crust.
Depending on the source used, iridium is either the rarest or third rarest stable element
in the crust, occurring at a mere concentration of 0.3 parts per billion.
Iridium along with other platinum group elements are far more common in large asteroids which
did not experience significant differentiation where heavier elements sunk into the core
of the object like on Earth.
The smoking gun came during the 1970s when a borehole was made off the coast of the Yucatan
peninsula when an exploration company hoping to find large underground oil reserves instead
discovered particles of shocked quartz which can be only formed in large amounts through
asteroid impacts.
Scientists later concluded that this shocked quartz existed as part of a layer within a
massive 180 kilometer or 110 mile wide impact crater that existed off of the Yucatan Peninsula.
66 million years ago, a large 19 kilometer wide asteroid was on a collision course with
Earth.
As the asteroid entered the upper atmosphere, it was travelling at a speed of 16 kilometers
per second or 36,000 miles per hour.
Animals who lived on the planet including T-Rexes 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 100 million megatons
of tnt occurred, as the asteroid struck a shallow continental shelf off of what is now
Mexico.
This powerful explosion pulverized a large section of water and crust over a vast area,
generating a magnitude 10.3 earthquake.
Due to the intense thermal radiation, any creature which could witness the fireball
immediately burst into flame, meaning everything in a 1600 kilometer radius.
A powerful shockwave soon raced outwards along with a 100 meter high tsunami, causing all
trees to be debarked and flattened in a 2100 kilometer radius.
This extreme damage traveled further, causing numerous trees to fall as tropical storm force
winds reached up to 6500 kilometers distant.
Large pieces of ejecta created by the impact then fell across the planet like falling lava,
starting large scale wildfires.
On the near opposite side of the planet, the impact triggered a near simultaneous increase
in the eruption of the Deccan Traps flood basalts.
Due to the immense amount of ash and pulverized material ejected, a several thousand year
long impact winter occurred around the globe.
Additionally, very minimal sunlight could reach the surface during this time, which
caused plants to die and many species which relied on them directly or indirectly to go
extinct.
This left behind a 180 kilometer wide impact crater which may have initially been 30 kilometers
deep at its center, punching a giant hole through the Earth's crust.
This hole would take tens of thousands of years, if not longer, to cool.
Thanks for watching!
If you would like to request a specific topic, please leave a comment below.
Additionally, if you wish to support this channel consider becoming a patron on patreon!