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Meteors, Comets,and Asteroids can have

Collisions with Earth


According to aUniversity of Arizona Chicxulub crater web page:

"... a large impact crater that is

65 million years old ... on Mexico's Yucatan Peninsula ... is called Chicxulub,

a Maya word that roughly translates as "tail of the devil." The crater, now buried beneath a kilometer-thick sequence of sediments, ... appears to have a diameter of 145 to 180 km, which makes it one of the largest confirmed impact structures on Earth. Only Sudbury in Canada and the Vredefort structure in South Africa could potentially be larger. ...

... The asteroid or comet that produced the Chicxulub crater was roughly 10 km in diameter. When an object that size hits Earth's surface ...[ as shown in this painting

from a National Museum of Natural History web page ]... it causes a tremendous shock wave while transferring energy and momentum to the ground. The impact was similar to a large explosion, although the energy of the Chicxulub impact dwarfs anything modern civilization has experienced. The energy of the impact was comparable to 100 million megatons of TNT, 6 million times more energetic than the 1980 Mount St. Helens volcanic eruption. The impact ejected rock from several kilometers beneath the surface of the Earth and carved out a bowl-shaped crater nearly 100 km in diameter. In addition, the shock of the impact produced magnitude-10 earthquakes, which were greater than the magnitude of any we have ever measured in modern times. ...[ According to a Miami University of Ohio web page: "... In contrast to the 2 to 3 cm thick clay layer found worldwide, the K-T boundary in the Gulf of Mexico region and in Haiti is composed of much thicker very coarse clastic deposits. Sand beds indicative of high energy deposition at the K-T boundary at Brazos River, Texas, have been interpreted to be the result of a major disturbance of the depositional environment, such as a tsunami approximately 50 to 100 meters high. ...". ]... The initial bowl-shaped crater was very unstable, and its walls quickly collapsed along a series of faults that enlarged the final diameter to between 145 and 180 km.  At the same time, the rock that had been compressed beneath the crater by the impact rebounded, producing a peak-ring structure in the crater's center. These dramatic changes, which rapidly transported huge volumes of rock over distances of tens of kilometers, occurred within only a few minutes. ...

... Because the impact site was in a shallow sea,

water rushed in to fill the circular depression. Kilometer high waterfalls tumbled over the rim of the crater and roared furiously across the floor of the crater.

Because seawater filled and covered the crater, sediment on the bottom of the sea soon buried the impact scar.  The crater is no longer visible today, even when standing directly over it.

In more recent times, the impact crater has affected the circulation of groundwater on the Yucatan Peninsula.  This groundwater, has in some areas, dissolved the limestone in the Yucatan peninsula.  Below ground, this has produced caves. At the surface, this has produced cenotes which are groundwater springs. The cenotes form a ring, like a blue pearl necklace, 

that is nearly coincident with the rim of the Chicxulub structure and is the only visible feature on the surface to indicate a huge crater lurks below. ...

... The explosion that produced the Chicxulub crater excavated a huge amount of material, which was then ejected upwards. Most of the debris was deposited as a blanket of material that covered North America and possible South America.  Near the impact crater the debris is tens to hundreds of meters thick, while as far away as Colorado (over 2000 km distance), the debris is still a centimeter thick ... Additional material was lofted in an expanding, vapor-rich plume that included gas from the vaporized asteroid or comet. This plume rose  far above the Earth's atmosphere, enveloping it, and eventually depositing a thin layer of debris around the entire world. ...".

According to aMiami University of Ohio web page:

"... the hi res image of the Chicxulub impact crater ...[shows]... a groove leading into the crater which shows the direction from which the asteroid or comet (rocky core type) hit. The hi res image covers the Yucatán Peninsula. Note the ejection plume pointing north and west out of the crater at the southwestern United States. ...

... The yellow arrow shows the hi res image of the Chicxulub impact crater itself imposed on a larger, lower resolution image of the Caribbean and Atlantic. ...

the Gulf of Mexico

owes its doubly arced shape to the K-T impact shockwave. ...

... there appears to be a gravitational anomaly (party dress pink) arc ... on the floor of the Atlantic Ocean off Florida ... which centers on the impact crater, as do several arcs in the Gulf of México. In fact, features such as the Alacrán Reef and Florida appear to be parts of the extended structure of the complex crater. The Blake Nose drill sites for cores of the K-T boundary are on the pink arc on the Atlantic side of Florida. ... This

is a hi res rendering of the gravity anomaly satellite image (Scripps Institute of Oceanography) that I mapped onto a sphere (MetaCreations's Bryce 4). Some concentric arcs centered on the Chicxulub crater are clear in the bright lavender tones of the image. At high resolution on the images downloaded from the Scripps Institution of Oceanography Geodesy site, there is radial and concentric cracking of the Pacific Plate centered on the impact site. ...".

Duncan Steel hypothesizes that the "...giant impact in Mexico apparently induced seismic waves which werefocused on western India, causing fracturing which then led to thewidespread Deccaneruptions. ...". Since India was then south of its presentposition, the Deccan basalt traps of India were then roughlyantipodal to the Chicxlub Yucatan crater.

According to anislandone.org web article released by Don Savage, and Diane Ainsworthof JPL, dated 28 December 1994:

"... it was the sulfur-rich atmosphere created in the aftermath of an immense asteroid collision with Earth 65 million years ago that brought about a global freeze and the demise of the dinosaurs. The impact of this large asteroid hit a geologically unique, sulfur-rich region of the Yucatan Peninsula in Mexico ... the impact kicked up billions of tons of sulfur and other materials and was between 10,000 to 50,000 times more powerful than the comet Shoemaker-Levy 9 impact on Jupiter last July. ... this asteroid was between 10 to 20 kilometers (6 to 12 miles) in diameter and its collision on Earth brought about total darkness around the world for about half a year ... But more importantly, persistent clouds generated by the impact on this geologically distinct region of sulfur-rich materials caused temperatures to plunge globally to near freezing. ... These environmental changes lasted for a decade and subjected organisms all over the world to long-term stresses to which they could not adapt in such a brief time span ... Half of the species on Earth became extinct as a result. ...

... it was the specific geological location of the impact in a region that is rich in sulfur materials that created catastrophic climate changes and led to the downfall of the dinosaurs. If this asteroid had struck almost any other place on Earth, it wouldn't have generated the tremendous amount of sulfur ... On impact, the asteroid hurled some 35 billion to 770 billion tons of sulfur high into the atmosphere, along with other materials.

The NASA team ... recently discovered rocks in Belize -- some the size of a small car -- that were blown out of the crater and landed south of the Chicxulub site. The boulder deposit in Belize also contained fragments of glass ... known as "tektites," ... The tektites have been found in other regions near the crater, such as Haiti, Mexico, Texas and Alabama, but never in association with large boulders. Another important find at the Belize rock quarry was limestone with fossils dating to the early part of the Cretaceous. ... Early Cretaceous fossils have been found deep below the surface near the crater during drilling by the Mexican Petroleum Company. We think the limestone found in Belize was excavated by the impact, which probably blew a hole more than 15 kilometers (nine miles) deep in the Yucatan Peninsula. ...

... The researchers used sophisticated atmospheric models of the sulfur-rich atmosphere of Venus to model their impact scenario. ... Initially, thick sulfur clouds, combined with soot and dust generated by this impact, would have spread worldwide and blocked out the Sun ... Night-like conditions probably existed all over Earth for at least six months essentially bringing photosynthesis to a halt.

Unlike the aftermath of typical impacts, the skies remained murky for at least a decade, due to chemically generated clouds of sulfuric acid high in the stratosphere. ... The reflection of sunlight back into space from these high-altitude clouds caused surface temperatures to drop to nearly freezing for many years all over the planet. ... These atmospheric conditions occur in Venus' perpetually cloudy atmosphere ... where ultraviolet sunlight and water in the high atmosphere can convert sulfur dioxide into sulfuric acid clouds. Sulfuric acid clouds like those that cover Venus may have continued to blanket the Earth for more than a decade after the initial impact of the asteroid, causing a secondary and more long-lasting effect which killed much of life on Earth. ...".

According to aFossil Cephalopods FAQ by Neale Monks:

"... Cephalopods ... evolved from primitive molluscs during the Late Cambrian, approximately 500 million years ago. Unlike the other molluscan groups, cephalopod evolution has concentrated not on a energetically connservative, defensive lifestyle but on mobility, dynamism, and intelligence. ...

... Cephalopods today are divided into the nautiluses, which reproduces many times, and the coleoids which reproduce only once (usually) ... The basic fact is that no ammonites are known beyond the end of the Cretaceous, while the other cephalopod groups, the coleoids and nautiloids, survive to the present day. This has been tied with other extinctions which occurred at the end of the Cretaceous (known as the Cretaceous-Tertiary, or K/T, boundary). ... How the squids and octopuses, which lived in the Mesozoic seas along with the ammonites, belemnites and nautiloids, survived is unclear. ...".

 


A Comet-Earthcollision about 250 million years ago caused the Permo-TriassicExtinction.

 


A Mars-sized body collidingwith Earth formed the Moon about 4,400 million years ago, perhapsleaving the Pacific Ocean as an impact crater and possibly formingthe initial continental crust of the Earth.

 


 

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