Professor explains meteor impacts

By Emily Khaykin

Like that of an earthquake, the shock wave that a falling meteor creates can be far more dangerous than the actual impact, leveling cities and whole forests of trees.

UCLA astronomy professor David Jewitt discussed the impact, both literally and causally, of meteors on the Earth in his lecture “Death from Space: Impacts, Extinctions, and General Devastation” during break on Nov. 1 in Ahmanson Lecture Hall.

Craters, formed by meteors, are identified by the types of minerals that are found inside them, most of which can only be formed in a high temperature and high impact setting.

Jewitt compared the amount of craters found on the moon with the amount of craters found on Earth.

“Because the surface of the Earth is relatively young and subject to erosion from the atmosphere, it shows less damage from craters than the moon,” Jewitt said.

An actual meteor, Jewitt said, is much smaller than its crater would suggest.

The kinetic energy from the impact blows out a greater volume of material, which creates the large hole that forms in the ground.

Examples of particularly high impact meteors that fell to the Earth’s surface have created Meteor Crater in Arizona and flattened surrounding forests in Tunguska, Siberia. The meteor that created Meteor Crater was about 50 million years old when it fell to Earth nearly 50,000 years ago at 150 million miles per hour.

The Tunguska Event happened more recently in 1908.

“Although the meteor exploded before contact [with the Earth’s surface], the impact from the explosion still managed to flatten over 2,000 square miles of pine forest,” Jewitt said.

Jewitt described the three major types of impacts that could occur from a meteor.

Local destruction is caused by the most common type of meteor, less than 100 meters in diameter. But the most deadly meteors are about one kilometer or more in diameter and can cause mass extinctions, much like the one that ended the Cretaceous Period.

“The event of a major impact is very rare, but it could influence the Earth’s climate and evolutionary cycle,” Jewitt said.