Tuesday, September 28, 2010
I often wonder why I am interested in so many things, and more importantly how these interests developed. In the case of meteorites, I believe I can trace it to the fascinating meteorite display in the Field Museum of Natural History in Chicago, and some summer nights watching some dramatic meteor showers light up the sky.
The earth is regularly struck by debris from space. It has been hit by about 130,000 meteorites large enough to produce a crater 2/3's of a mile wide. Although this kind of impact site is visible on the moon, earth is so geologically active that evidence of many impacts have disappeared. So far, more than 160 impact sites have been identified worldwide, with new craters discovered every year.
Most meteorites are fragments of asteroids, though some are produced when asteroids hit the surface of the moon or mars, flinging debris into space. When they are outside the atmosphere these rocks are meteoroids, while those that enter the atmosphere are meteors. These are usually so small that they burn up as they plunge toward earth, leaving a bright trail in the sky, often called a shooting star. Meteorites are objects large enough to travel through the atmosphere and hit the ground. If they are the size of a house or larger they blast out a crater.
The first major impact structure to be identified was Meteor Crater in Arizona, with its distinctive bowl shape. It is the result of the most recent significant meteorite impact on earth.
When a meteorite strikes the earth, the impact sends shock waves through the ground, squeezing the surrounding rock to two, or three times its normal density. The compressed rock then springs back, shattering into fragments, hurling chunks upward, and outward, along with pieces of the meteorite that have not yet vaporized. The result is a bowl shaped crater that is much larger than the meteorite.
The potential energy of a significant meteorite impact on the earth is more than one hundred million megatons-more than the world's entire nuclear arsenal.
Buried deep beneath the limestone of Mexico's Yucatan Peninsula, Chixulub is one of the largest meteorite cImage via Wikipediaraters found on earth. The impact was catalclysmic: fires raged over the surface, giant tsunamis radiated across the oceans, and the planet was rocked by massive earthquakes. Many scientists believe that the devastating global effects of the Chixulub impact caused the extinction of the dinosaurs. They believe that debris from the impact was suspended in the atmosphere. This would have blocked out the Sun's rays, turning the world ice cold, and spelling doom for the dinosaurs.
Much of the information for this post comes from the Smithsonian Institution's book called Earth.
Friday, September 17, 2010
Morrill Hall, one of the oldest buildings on the Michigan State campus, is set to be demolished in 2013, and its classrooms, and offices moved to a new addition of Wells Hall. Ground was broken for that new addition earlier this week. To commemorate Morrill, plans are to restore the area to a park, with a plaque and part of the stone or brick of Morrill Hall.
My first thought was we should save this building as it is a major part of Michigan State's history. But, some investigation finds that the place is deteriorating with the floors and ceilings tilted and the place infested with cockroaches and bats, so maybe the history, English, and religious studies departments will be better off in their new home in Wells Hall.
Image via Wikipedia
A little history: It was dedicated in October 1900, and known as the Women's Building, and as its name implies was built to house women. At the time of the dedication it housed 120 women students, and had cooking laboratories, and a large gymnasium, as well as the dorm rooms. In 1937, the name was changed to Morrill Hall and it became a liberal arts division center. The new name honored the Morrill Act of 1862, which laid the groundwork for the land grant colleges providing university funding by the government, and built on federal land.
My main memory of Morrill Hall is from spring term of freshman year, when for some reason now forgotten I decided to drop an economic course a couple of weeks into the term. The course was taught by one of the most popular professors on campus, but one who had a reputation for being foul tempered and mean. I announced at dinner that I was headed to Morrill Hall for a face to face with the professor. The reaction I received was pretty much, 'You are really going to get blasted." This girl I had been dating (Leslie) came with me for support, or maybe out of curiosity. I remember the long slow walk up the four flights of stairs, and knocking on the door. I survived. He basically told me I would be stupider for not taking his class, and would live to regret it, but he signed the paper, and I shot out of there
.Some early Women's Building Residents.
Earlier this week Leslie and I went into Morrill and shot some pictures: