Geography
of Prospect Park East River Road Neighborhood
Notes from a neighborhood presentation by Karen Murdock, 2008-05-08.
Physical Geography: Various Rock Layers
Platteville Limestone
Glenwood Shale - an aquitard (doesn't hold water); the "perched water" above the shale may flow out as springs.
St. Peter Sandstone - an aquifer (holds water)
from Wikipedia entry for "aquifer": "An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include: an aquitard, which is an impermeable layer along an aquifer, and an aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. The surface of saturated material in an aquifer is known as the water table."
Last Ice Age
The last Ice Age 12,000 years ago created most of our environments — glacial geography. Tower Hill is a "kame" - old English for "mound of sand and gravel deposited by a glacier." The rest of Prospect Park is glacial till.
Mississippi River Gorge formed by retreating water falls, a transient feature. The falls were at Ft. Snelling 12,000 years ago, and at Prospect Park 3-4,000 years ago. They are now St. Anthony falls.