SandstoneThis rock is a cross-bedded sandstone from the Triassic of Poland. The Triassic was the tim
SandstoneThis rock is a cross-bedded sandstone from the Triassic of Poland. The Triassic was the time of Pangaea; the mountain ranges it was built by continental collisions more than a hundred million years before this rock formed. The combination of a huge supercontinent and low sea levels led to dry conditions in the part of Europe that would eventually become Poland. During these dry times, deserts developed in many parts of the world, including this site. Sand grains were blown around on the wind, tumbling over the backside of sand dunes. The sand tumbling down the slopes created the dipping beds known as cross beds, and when the sand dunes passed they left behind the flat layers. Image credit: http://bit.ly/2zobTJiReferences:https://gq.pgi.gov.pl/article/view/20767http://dml.cmnh.org/2015Oct/msg00071.html -- source link
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