Snowball Earth Educational Rock Sample Suite 17 by Robin Rohrback-Schiavone

Sample 17 is a striated and faceted stone embedded in a sandy diamictite matrix. The erosional surfaces of the pebble suggest that it was in direct contact with mobile basal ice. The flattened (faceted) surfaces of the pebble were formed as the pebble scraped along the bedrock beneath the moving basal ice. The striations that appear as parallel grooves etched into the faceted surface of the pebble record the direction of ice movement.

This sample is from the Storeelv Formation in eastern Greenland.

The sample is 10 cm across at its widest point.

This sample is from the Snowball Earth Educational Rock Sample Suite, and comes courtesy of Paul Hoffman, Harvard University; Eugene Domack, Hamilton College; and Timothy Fox, Hamilton College.
For more information on the Snowball Earth Educational Rock Sample Suite, visit www.snowballearth.org/samples.html  Will open in a new tab or window

Image made as part of the MAGIC project (Mid-Atlantic Geo-Imagery Collection) using Northern Virginia Community College's gigamacro rig, as seen here:
gigamacro.com/gigapixel-macro-imaging-system / Will open in a new tab or window