This EarthCache will cover two of these contributing factors.
The Sea and Glaciers.
This area that you are standing right now is called the Paleozoic Plateau.
Any sandstone that you encounter in this area originated as sediment on tropical sea floors between 300 and 550 million years ago.
The formation of sandstone involves two principal stages. First, a layer or layers of sand accumulates as the result of sedimentation, either from water (as in a stream, lake, or sea) or from air (as in a desert). Typically, sedimentation occurs by the sand settling out from suspension; i.e., ceasing to be rolled or bounced along the bottom of a body of water or ground surface. Finally, once it has accumulated, the sand becomes sandstone when it is compacted by pressure of overlying deposits and cemented by the precipitation of minerals within the pore spaces between sand grains.
Much later (14,000 - 70,000 years before the present), several different glacial advances covered different parts of Iowa and buried most of the sedimentary bedrock foundation from view. Materials near the land surface accumulate during glacial episodes. These materials include loess (deposits of wind-blown silt) and alluvium (sand and gravel transported by glacial meltwater streams and rocks transported by the glaciers themselves).
These rocks that you will encounter that were deposited by glacial processes are granite.
Granite is an igneous rock and is formed from magma. Granite is not native to this area, these rocks were carried to their current locations by glacial ice, often over hundreds of miles.
To receive credit for this EarthCache, you will visit two waypoints and apply what you have learned to identify the rock present.
1. At the posted coordinates-
Identify this rock type.
Of the three main rock classifications (Igneous, Sedimentary, and Metamorphic), what type is this?
2. Now move to
N40 49.206 W092 35.462-
Identify this rock type.
Of the three main rock classifications (Igneous, Sedimentary, and Metamorphic), what type is this?
3. Now, using what you learned in this EarthCache's write up, which of these two rocks
"arrived on the scene" first?
I would like to thank Ron Moore-Lake Wapello State Park Manager,
for granting me permission to develop this EarthCache.
