Today, geologists find yet another major meteorite/asteroid strike. We can see from the moon and other planets that these events happen all the time. I will suggest all the sudden evolutionary changes that punctuate the fossil record may all be caused by celestial objects suddenly changing the ecosystem too fast for many creatures to easily evolve to accomodate these changes.
By Paul Rincon
Science reporter, BBC News, Houston
A seismic survey peels away the sediments to reveal the structure
Oil exploration work in California's Central Valley region has uncovered a possible space impact crater.
The 5.5km-wide bowl is buried under shale sediments west of Stockton, in San Joaquin County, and is thought to be between 37 and 49 million years old.
Data from a 3D seismic survey of an ancient sea bed clearly shows a circular structure buried 1,490-1,600m (4,890-4,250ft) below sea level.
The Victoria Island structure, as it has been named, has a concentric rim surrounding a "central uplift" - a peak at the centre - which are both characteristic of impact craters.
This happened when Central California was in the ocean and it probably raised quite a huge tsunami as well as vaporizing a lot of ocean floor and water itself. This would be a sudden, very abrupt change in the climate and the reverberations would have lasted for quite a few years.
We can clearly see from the dramatic fossil record that aside from the very, very big extinction events which everyone has accepted, the Permian and the end of the dinosaurs, we have many 'mini' extinction events and as geologists find more and more hidden strike zones, it is notable that they occured when other, smaller extinctions and dramatic, SUDDEN changes occured.
Unlike the slower evolution over time as temperatures rise or fall or continents move slowly over the equator and then over the poles, these many day/night changes the punctuate the history of life whereby a teeming ecosystem suddenly collapses and mostly the smaller species survive and begin to proliferate and fill all the empty niches.
One of the worst cosmic collisions known to have rocked what is now the United States carved a huge crater from the present-day mouth of Chesapeake Bay.
The asteroid or comet impact kicked a cloud of debris high into the atmosphere, spawned devastating tsunami waves up to 2,000 feet (610 meters) high, and carved out the largest crater ever found in the United States, researchers say.
It also left a legacy of salty groundwater that threatens the fresh water supplies of some 2 million people who live in and around the unstable crater eons later.
The water woes started when a huge object slammed into Earth 35 million years ago. The impact left a now-buried, unstable crater rim that still generates earthquakes as it shifts and sloughs around.
"The asteroid or comet probably measured about 1 to 2 miles (1.6 to 3.2 kilometers) in diameter and was traveling at tens of miles per second," said Greg Gohn, USGS Chief of the Chesapeake Bay Impact Crater Project. "It gouged a crater 53 miles (85 kilometers) wide and fractured bedrock to a depth of well over a mile. Today, those disrupted rock units greatly affect the pattern of groundwater flow throughout southeastern Virginia."
Perhaps meteorites that hit land don't have the strong effect of the ocean strikes for various reasons. For example, the continental thickness may respond differently from ocean floors which are perhaps thinner and so the lithosphere is much more affected. Also, there is no extra water added to the atmosphere suddenly and I do know that sudden global flooding would create tremendous habitat damage whereas simple dust and dirt would cool things down but not wash away whole ecosystems.
On top of all this, I am certain volcanic action across the planet would cause lots of side-events, maybe even things like the Siberian Traps which coincided with the strike in Antarctica at the beginning of the Permian Extinction or the Deccan Traps which happened perhaps the same way in the later extinctions.
Close to 23 million years ago, a great flaming rock fell from the sky. It slammed into the arctic and left a steaming crater 20 km across. It was not the largest object to have crossed Earth's path, nor was the impact the only one of its time. But for life on Earth, the rock had found the worst possible place to crash into.
The area surrounding the impact was undoubtably devastated immediately. Thick clouds of ejecta in the air would have stalled photosynthesis across much of the Northern Hemisphere, breaking down food chains across North America and Eurasia and leading to the starvation of millions of animals. As devastating as this catastrophe must have been, the scorching of the sky was not the most serious consequence of the collision. The blast of the impact had, after vapourising the surface sediments, encountered bedrock rich in anhydrite (calcium sulphate) and various carbonates. Great quantities of this material, some from over 1.7 km deep within the Earth, was thrown into the atmosphere where it lead to an increase in greenhouse gases and deadly falls of acid rain.
On both Spec and, RL the eroded scar of the 23 million year-old impact, known as the Haughton crater, sits in the high arctic of North America (75°22'N, 89°41'W). The effects of the impact on RL's Cenozoic biosphere is still being investigated and it has been implicated in a number of regional extinctions. What is certain however, is that no megafaunal extinction event of the magnitude of Spec's decimated northern dinosaur faunas occured in our native timeline.
Namely, the strata in the rocks often change with the fossils...quite abruptly. And at significant times, across many ecosystems in many areas simultaneously. A sudden change in percipitation can cause tremendous, swift changes in the landscape and a place that was, say, a fertile valley or a rich swamp, can instantly, in one year, be covered over with tons of sand or mud or other run-off items which we see over and over again in the geological record.
(AP) Researchers studying rocks from Antarctica have found chemical evidence that a huge meteorite smashed the Earth 251 million years ago and caused the greatest extinction event in the planet's history, killing about 90 percent of all life.
The extinction, which scientists call the Permian-Triassic event, came some 185 million years before a similar meteorite collision with the planet killed off the dinosaurs.
"It appears to us that the two largest mass extinctions in Earth history ... were both caused by catastrophic collisions" with meteoroids, the researchers say in their study appearing this week in the journal Science.
And these are so obvious but when it comes to the other obvious events when the world suddenly dropped the ball on a host of previously successful species and suddenly veers off in a totally new direction, these happenstances are not singular at all but are COMMON.
Department of Systematic Botany, Evolutionary Biology Centre, Uppsala University, Sweden. email@example.com
Phylogenetic interrelationships among all 18 families of Poales were assessed by cladistic analysis of chloroplast DNA rbcL and atpB sequences from 65 species. There are two well-supported main clades; the graminoid clade with Poaceae (grasses), Anarthriaceae, Centrolepidaceae, Ecdeiocoleaceae, Flagellariaceae, Joinvilleaceae, and Restionaceae; and the cyperoid clade with Cyperaceae, Juncaceae, and Thurniaceae. A sister group relationship between Poaceae and Ecdeiocoleaceae is identified with strong support.
The sister group of this pair is Joinvilleaceae. These relationships help in elucidating the evolution of grasses and the grass spikelet. Dating of the tree was done by nonparametric rate smoothing of rbcL molecular evolution. Most Poales families date back to the Cretaceous >65 million years ago (mya). Dispersal-vicariance analysis indicates that the Poales originated in South America, the cyperoid clade in West Gondwana (South America or Africa), and the graminoid clade in East Gondwana (Australia). The Trans-Antarctic connection between South America and Australia, and its breakup about 35 mya, probably influenced the evolution of the Poales and the graminoid clade in particular, leading to vicariance between the continents, but the separation of Africa from the other Gondwanan areas, completed about 105 mya, is too old for such a relation.
We know precious little about the evolution of grass but we do know this coincided with the rapid evolution of horses and cows and other grass-grazing hoofed mammals who were all insignificant parts of the pre-strike ecosystem. And most of the big tree grazers vanished without any chance to evolve within the new world order!
Let's look at horses: looking at their early shape, they were furtive, small creatures with fairly big feet compared to their tiny bodies, splayed toes such as swamp animals or creatures living on very spongy ground would have. We are fortunate to see close-up their evolution from the very small, shy creatures to the plains-dwelling, grass eating running in large herds, large mammals. Why would they leave the swamps and dense growth places to run on plains?
Perhaps, in the catastrophe of this lesser-extinction event, the sudden floods coupled with a total change in the lay of the land meant their previous habitat was ruined and only mutant forest-proto-equines survived while the older, earlier models were literally swept away by floods.
The survivors had to be the ones not living next to streams of lowlands but the ones that were on the fringes of the forests and thus, were not swept away. But their food source dried up or was covered by dirt so they fended for themselves, eating stuff that was hard to digest or chew.
The survivors of this harsh environment passed on stronger teeth, feet that could run on hardened mud and stomach parasites that could break down the thick, nearly indigestible fibers of a plant that had few takers previously: the earliest grasses.
All the grass-grazers and the grass itself evolved rapidly in tandem, taking over much of the earth. We now have bamboo, rice, wheat, sugar cane and all sorts of grasses all over the earth and we exploit them very heavily for our own eating. This new life-form is disliked by all the other monkey/primate family, for example. They would all rather eat insects than any grass form. But the grass eaters triumphed rapidly and dominate the earth, quite literally.
If we were unable to eat grasses, we would not be so great a population today, for example. Using our brains, we figured out how to eat grass too. And this gave us tremendous power over the environment.
The grass grazers nearly all developed an important device the grasses need in order to colonize the hard-mud areas devastated by meteorite strikes: hooves. As a person who owns grass grazers and cares for fields, the sharp hooves break up the hard soil and 'plows' it for the grasses. If the grazers don't chop up the dirt, the roots of the grasses get too entangled and they strangle themselves. When I want more grass to grow, I take out the tractor and tear up the pastures and then reseed them. Indeed, the strength of grasses both in the roots and the seeds.
All the grazing animals graze different levels of grass: cattle prefer the tops, horses, the middle and sheep the stubs. Put sheep in a deep-grass pasture and they will be unhappy until they trample it in. Put a cow in a cropped field and it will starve. Horses will jump fences for their own prefered grassing rights.
We are in the Age of Grazing Grasses. Humans and the various animals that graze on grasses control the environment in many places, sometimes very ruthlessly. The hunters and eaters of grazers also rule. And the jungle/tree environment is in retreat.
In the great plains, few trees grow simply because the grazers will mow them down long before they pass sapling stage. In winter, the grazers will strip the bark, they trample the saplings into the earth and this vastly changed the earth. Instead of vast forests and fens, we have grassy plains that stretch for thousands of miles.
Grasses cannot colonize forests. They can only do this when forests are destroyed and then, only if there are sharp-hooved grazers ruthlessly removing all potential trees. This happened before the first Ice Age. And humans, very early on, felt an affinity with the grazers on the grassy plains.
Ejected from the Garden of Eden jungles, we stood up and began to follow the new herds that had so violently changed the planet. We became the herders and the sower of the seeds of these grasses. Possibly the very first thing ever made by humans that wasn't either a stick nor a stone was some woman weaving a sling out of grasses or rushes for her baby.