At the end of the Ice Age, the last ice sheet began to melt back from the New York City region about 14,000 years ago, leaving behind a layer of clays, sands and pebbles, as well boulders known a glacial erratics. Glacial Erratics are made up of rock materials not generally found in their immediate surroundings.
This large boulder, found in the Native Plant Garden at the New York (Bronx) Botanical Garden — known as Split Rock — is a glacial erratic.
Split Rock is composed of Yonkers gneiss, which is different from the local bedrock. The split in this boulder was likely caused by an ancient freezing and thawing cycle thousands of years ago.
Photographed on New Year’s Day, 2020!
Update August 15th, 2020: We just got home from visiting the NYBG, which has recently reopened after being closed since March due the Covid 19 Pandemic. It was great to be back! I snapped a couple of new photos for this post which show the Split Rock amid the summer flora! Enjoy!