Prehistoric Scratchpad
Park on the St. Croix River between Minnesota and Wisconsin. One of the few areas rock formed during the volcanism of the Midcontinent Rift System are exposed. These rocks straddle the St. Croix River Valley, formed when the glaciers of the last ice age melted.


1 Billion Years AgoEdit

The Interstate Park was covered with the basalt that was formed from the volcanic eruptions from the Midcontinental Rift System, which had closed up.

Earlier HistoryEdit

The Midcontinental Rift System caused volcanic eruptions that sent magma through this area 1.1 Billion Years Ago. This rift failed to split open the continent and closed up after 15-22 million years later.

Between HistoryEdit

During the Furongian epoch of the Cambrian period, this site was covered by a shallow sea, which deposited sandstone and siltstone atop the basalt (epoch originally called the Croixian in North America).

10,000 Years AgoEdit

The St. Croix River Valley was being formed by torrents of water flowing south from the melting glaciers. Glacial potholes formed as the whirlpools in the Glacial St. Croix River dug into the ground The Glacial Gardens contains the greatest concentration of Glacial potholes in the world, and includes the Bottemless Pit, the deepest explored one in the world.

Later HistoryEdit

Modern HistoryEdit


Interstate Park Web PagesEdit

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