This semester, a troop of Gusties is trekking around Sweden under the leadership of Jeff and Maria Jeremiason. On the trip are two Geo majors (and I hear rumors of a newly-recruited third??); below is a missive from Ruby Schaufler (Geology, ’17) and Lindsey Reiners (Geology, ’17).
But first, here are Ruby and Lindsey with our beloved Mark Johnson! He claims this is a peneplain; I’ve told him I’ll require a personal site visit before I will be convinced. And also, here’s a pic of Maria and Jeff, honorary geologists, in a rock. Always a good place to be.
From Ruby and Lindsey: On Wednesday February 25th, the Semester in Sweden class became a team of Geologists. We started at 8:15 in the morning and were on our way with Swedish geologist Kirsten to see the Siljan Ring formation. The Siljan Ring is a ring of lakes formed by a meteorite that hit 377 MA.
How it works is best explained by this diagram.
The bed rock here is granite with a thick layer of limestone on top. When the meteorite hit, the limestone turned inward toward where the meteor hit. Due to rebound from the impact, the spot where the meteor hit is uplifted. That is the land in the center of ring of lakes. When the last ice age occurred, all the limestone was scraped off the surface and granite was exposed. The only limestone remaining is what was pushed down into and around the lakes.
Today, you can see the superpositioned limestone with its layers vertical or tilted instead of horiontal.
On our excursion we saw limestone quarries and a limestone factory. One of the old quarries was turned into an outdoor concert hall, but we were not able to see it. A few of us found fossils and on some of the limestone you could see the black petroleum from all of the organic matter.
A fun place we stopped at was Boda Church that was built with limestone floors. The fossils in the floor were so big that in the isles of the church they covered them with sand and rugs so the elderly could walk comfortably on the floor. It is a shame they had to cover them because the fossils are truly amazing.
Ruby and I miss all you rock heads in the basement!
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