What evidence supports the asteroid impact hypothesis?
To test the hypothesis that an asteroid impact caused the K-T mass extinction, key evidence included impact ejecta, tsunami debris, and careful gravitational field measurements.
What caused the Cretaceous Tertiary mass extinction?
As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastated the global environment, mainly through a …
What piece of evidence initially convinced Dr Alvarez that a mass extinction had occurred at the KT boundary?
What piece of evidence initially convinced Dr. Alvarez that a mass extinction had occurred at the K-T boundary? There were many different foram fossils below the boundary between the Cretaceous and Tertiary periods and fewer above the boundary, which means that the boundary marks the time of the mass extinction. 2.
What is the difference in the foraminifera from the Cretaceous period below the KT boundary and the Tertiary period above the KT boundary )?
Differences scientists saw in the foraminifera found in rock layers above and below the K-T boundary. Below: foraminifera fossils were larger and more diverse. Above: most foraminifera fossils disappeared; surviving species were smaller. Alvarez published his paper showing high iridium levels at the K-T boundary.
Why is the KT Boundary important?
The K-T boundary separates the age of reptiles and the age of mammals, which was first recognized over one hundred years ago by geologists who realized that there was a dramatic change in the types of fossils deposited on either side of this boundary.
What is an alternative hypothesis for the high levels iridium in the KT Boundary Why was this hypothesis dismissed?
4. What is an alternative hypothesis for the high levels Iridium in the K-T boundary? Why was this hypothesis dismissed? A supernova explosion but was debunked because it was a 1 in a billion chance of a supernova happening that close to earth.
How deep is the iridium layer?
The thickness of the layer appeared to be 3-4 cm. The iridium-rich layer at the K-T Boundary has been associated with the Chicxulub Crater centered off the Yucatan Peninsula of Mexico, for which a strong case has been made for an asteroid impact that contributed to the observed mass extinction.
How old is the KT boundary?
66 million years
Why is Iridium common in asteroids?
Because it is very dense, and bonds well with iron. As a result, almost all of the iridium on Earth sunk down into the core while our planet was still molten, just after its formation. So any given chunk of an asteroid is likely to have about as high a percentage of iridium in it as the original dust cloud did.
What is a iridium spike?
The iridium is present only in the boundary rocks and therefore was deposited in a single large spike: a very short event. Iridium occurs in normal seafloor sediments in microscopic quantities, but the iridium spike at the K-T boundary is very large.
Is Iridium rare on Earth?
Today, iridium is commercially recovered as a byproduct of copper or nickel mining. Pure iridium is so rare on the Earth’s crust that there is only about 2 parts per billion located in the crust, according to Chemistry Explained. “Iridium is one of the densest and rarest of Earth’s natural elements.
Where is Iridium most commonly found today?
Iridium generally is produced commercially along with the other platinum metals as a by-product of nickel or copper production. Iridium-containing ores are found in South Africa and Alaska, U.S., as well as in Myanmar (Burma), Brazil, Russia, and Australia.
How thick is the KT boundary?
4 to 16 cm
What element was found in the thin layer of clay?
How did climate change cause some of the mass extinctions?
A massive extinction event that took place 200 million years ago may have been caused by climate change, new research suggests. The findings shed new light on the pace of mass extinction, and imply that relatively small changes in atmospheric carbon dioxide levels may be enough to trigger an extinction event.
Why did scientists first hypothesize that extraterrestrial impact caused the extinction at the KT boundary?
37) Scientists hypothesized that the Mass Extinction at the K-T boundary was due to an asteroid impact by looking at the rock record without actually finding a crater.
How might a major asteroid impact have caused a mass extinction?
The way this works is through climate change. When a really big asteroid hits the Earth, it is not the impact that kills, it is what comes after. When temperatures cool, the whole Earth’s ecosystem is messed up. Plants and animals that can’t tolerate the lower temperatures for long periods of time go extinct.
What are some oceanic phenomena caused by the KT impact?
That seismic activity caused huge landslides on the seafloor, ripping through any colonies of life. The Chicxulub impact into the Gulf of Mexico, over the partially submerged Yucatán Peninsula, created a radiating series of waves, including tsunamis that ramped up and towered over coastlines.
What are the factors that affect the size of an impact crater?
The size and shape of a crater depend on several factors:
- the mass of the impacting object;
- the density of the impacting object;
- the velocity of the impacting object; and.
- the geology (type of rock) of the surface the object strikes.
Which one made the deepest impact crater?
The Vredefort crater /ˈfrɪərdəfɔːrt/ is the largest verified impact crater on Earth. More than 300 kilometres (190 mi) across when it was formed, what remains of it is in the present-day Free State province of South Africa.
How is a impact crater formed?
An impact crater is formed when an object like an asteroid or meteorite crashes into the surface of a larger solid object like a planet or a moon. To form a true impact crater, this object needs to be traveling extremely fast—many thousands of miles per hour!
How does the angle of impact affect the crater size?
In case of large impact craters, collapse of the central peak is more pronounced in the downrange direction. Effect of the impact angle on crater size: Crater size decreases proportional to the sinus of the impact angle α . This decrease is more pronounced for stronger materials.
How do you determine crater size?
- Crater depth can be calculated from the shadow length as before.
- Upload the image into HiView and use the measuring tool to.
- count the pixels.
- Use the shadow formula.
- d= tan(90-θ) X L.
- d = tan(90 – 72) x (1899 x 25) cm.
- d = 15425 cm = 154 m.
How does drop height affect crater size?
The higher the drop height, the greater the velocity of the ball. At any given height, the most massive ball will have the greatest effect. The greater an object’s velocity, the larger its impact crater. When dropped from a given height, the greater the mass, the larger the crater.
How do you determine the age of a crater?
Counting the Craters One way to estimate the age of a surface is by counting the number of impact craters. This technique works because the rate at which impacts have occurred in the solar system has been roughly constant for several billion years.
How do they determine the age of the planets?
To find your age on the outer planets (Jupiter, Saturn, Uranus, Neptune, and Pluto), divide your age in Earth years by the approximate length of the planet’s year in Earth years. This is your “new” age. For example, a 20 year old on Earth would only be 1.7 years old on Jupiter because 20 / 12 = 1.7.
Which planet has the oldest surface?
How can we use impact craters to estimate the age of a planetary surface?
How can craters be used to determine the age of a planet or moon? Scientists record the size and number of impact craters — and how eroded they are — to determine the ages and histories of different planetary surfaces.