The James River - Eastern South Dakota EarthCache
sdgal: The James River has flooded too many times in the past 3 years. For safety reasons I'm going to archive.
The James River - Eastern South Dakota
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The James River is prone to flooding in the spring therefore, GZ may not be approachable if the water is too high.
South Dakota can generally be divided into three regions: eastern South Dakota, western South Dakota, and the Black Hills. The James River Valley is one of the major geographical features of the Eastern South Dakota region, and its topography was primarily formed by glacial action. The James River Valley is a broad, nearly level stretch of land from 50 to 75 miles wide and 250 miles long within South Dakota. It has an overall length of 710 miles and a drainage basin of 22,000 square miles running from deep in North Dakota. In South Dakota the James River is often prone to spring flooding due to the fact that it drops only a small amount in each mile that it flows southward.
James River Valley – Glaciers
The surface rocks in the east river area of South Dakota and the James River Valley tell the story of glaciations. Glaciers did not exist continuously through what was called the Ice Ages. The glaciers both eroded and deposited rocks as they covered the land and then receded. The highly irregular features of the hill country above the river valley are the result of glaciers leaving behind clay, sand, and gravel as they melted. This is how geologists read the prehistory of the area.
Geologists know that four major periods of glaciations took place. It is believed that eastern South Dakota had traces of all four glaciers. Between the glacial ages there was enough time and favorable conditions for life to reestablish itself. The climate warmed, soils formed, and animal and plant life invaded the area. Evidence of this shows up in the different layers created by a glacier of almost unimaginable size as it moved over what is now eastern South Dakota. At its greatest depth in northern South Dakota, the glacier was one thousand six hundred feet from top to bottom. The glacier scraped every square foot of earth with 45 tons of pressure. When it moved, at the rate of a couple inches per day, it bulldozed the land, forming nearly every noticeable geographical mark that can be seen in the region today.
At the end of the last glacier, about 8000BC, the melting water of the ice formed a large lake which occupied much of the present James river lowland north of the Yankton area. It also left the Heartland Region sitting atop three major aquifers. Before the glaciers, the rivers of South Dakota flowed mainly west to east, therefore there was no Missouri River. With later glaciers, drainage was forced around the western edge of the glacier creating the present location of the Missouri River flowing to the south.
Eastern South Dakota generally features higher precipitation and lower topography than the western part of the state. Smaller geographic regions of this area include the Coteau des Prairies, the Dissected Till Plains and the James River Valley. . . The Dissected Till Plains, an area of rolling hills and fertile soil that covers much of Iowa and Nebraska, also extends into the southeastern corner of South Dakota. Layers deposited during the Pleistocene epoch, starting around two million years ago, cover most of eastern South Dakota. These are the youngest rock and sediment layers in the state, and are the product of several successive periods of glaciation which deposited a large amount of rocks and soil, known as till, over the area.”
The Glaciers Advance
The unconsolidated rocks making up most of the surface east of the Missouri River are of glacial origin. Evidence suggests that these sediments were laid down through numerous glacial advances and retreats beginning some 1.5 million years ago, and ending 10 thousand years ago. Rock particles of many types, shapes, and sizes were left behind by the glaciers, and this material is collectively called drift . Many of these rock fragments originated from Canada and other points north and east of their present positions. The average thickness of the glacial sediments in Eastern South Dakota is about 100 feet (30.5 meters), although in the northeastern part of the state thicknesses can sometimes exceed 900 feet (274.3 meters).
Requirements:
1) Post a picture of you or your group with your GPS at the posted coordinates. UPDATE: Picture is optional.
2) Send your answers to the following questions to me via my profile address:
a) What is direction of the river flow adjacent to GZ? (Viewed from the cache coordinates.)
b) What is the elevation at the posted coordinates?
c) If the elevation of the James River is 1302 feet at the ND/SD border, what is the drop of the river per mile from the ND border to GZ? Assume it is 212 miles from the ND border to GZ.
Additional Hints
(No hints available.)