Why did he test for iridium in the clay of the K-T boundary?
Why did Luis Alvarez suggest measuring iridium levels in the K-T boundary? He was looking for a way to determine how quickly the layer had been deposited. The scientific community was slow to accept the asteroid impact hypothesis.
What is a KT layer?
Definition of K-T boundary : the transition between the Cretaceous and Tertiary periods of geologic time characterized by a mass extinction of many forms of life including the dinosaurs also : a geologic stratum marking this boundary.
What was so special about the KT layer?
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 does the presence of so much iridium in the KT clay layer mean?
The term iridium anomaly commonly refers to an unusual abundance of the chemical element iridium in a layer of rock strata at the Cretaceous–Paleogene (K-Pg) boundary. The unusually high concentration of a rare metal like iridium is often taken as evidence for an extraterrestrial impact event.
What is significant about the discovery of iridium at the K-T boundary?
Iridium is rare on Earth because it sank down into the center of the planet as it formed, but iridium can still be found in large concentrations in asteroids. When they compared the concentrations of iridium in the K-T boundary, they found it matched the levels found in meteorites.
What does kt stand for in KT extinction?
Cretaceous-Tertiary Mass Extinction event
Paleontologists speculated and theorized for many years about what could have caused this “mass extinction,” known, as the K-T event (Cretaceous-Tertiary Mass Extinction event).
What is the K Pg boundary made of?
In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth’s crust, but abundant in asteroids.
What caused the KT extinction?
Many scientists believe that the collision of a large asteroid or comet nucleus with Earth triggered the mass extinction of the dinosaurs and many other species near the end of the Cretaceous Period.
Why did Luis Alvarez test for iridium?
Luis believed that neutron activation analysis would help determine how long it took for the clay layer to form. To the surprise of everyone involved, the measurements by Asaro and Michel showed that the clay layer was about 600 times richer in iridium than the surrounding limestone.
Where is iridium found?
Iridium-containing ores are found in South Africa and Alaska, U.S., as well as in Myanmar (Burma), Brazil, Russia, and Australia. In the late 20th century South Africa was the world’s major producer of iridium.
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.
What is the concentration of iridium in the iridium layer?
Iridium normally is a rare substance in rocks of Earth’s crust (about 0.3 part per billion). At Gubbio the iridium concentration is more than 20 times greater (6.3 parts per billion), and it exceeds this concentration at other sites.