This EarthCache highlights an interesting geological feature of Oldham County, Texas. There is plenty of room to pull your car over to the side of the road at both waypoints, and you don’t need to leave the side of your car to make the observations needed to complete the logging tasks.
What you are looking at straight ahead of you is a rock formation that is the only trace of an old bed of the Canadian River, which now runs about a mile to the north. Locals call it Saddlehorn Hill.
Rivers carve out their beds in local rock and deposit those sediments along the way especially anywhere that they slow down. Riverbeds, then, tend to be made of hard material. If the river shifts its course, the old riverbed might be harder than a lot of the surrounding countryside, and so traces of it can be found hundreds, and even thousands, of years later.
As it crosses the Texas Panhandle’s dry and sandy plains, the Canadian River meanders along in wide, slow, braided loops. Sometimes a strong enough storm or flash flood can make the river override its banks and flow towards the closest point downstream, leaving a loop cut off from the main channel. The loop eventually dries up.
To claim a find on this Earthcache, you need to complete two tasks—there is a third, optional task, as well.
First task: straight or curved?
If the river ran straight through this section, what’s left of the two banks would most likely be of fairly equal height. But when a river curves, the water moves faster along the outer edge, carving away more earth and rock without depositing much sediment—this bank will be the steeper one. Along the inner edge, the bank usually has a gentler slope—it has had river sediments deposited there by slower moving water.
Questions: Do you think that what’s left of the river bed before you is part of a straight section or a curve? If it was part of a curve, which side was the outer edge, and how can you tell?
Second task: How much of the old floodplain has eroded away?
The Canadian River has been eroding away the dry lands of the Texas Panhandle for thousands and thousands of years. Over time, the elevation of most of the area has dropped except where a place like Saddlehorn Hill has resisted that erosion. The old riverbed is therefore higher than the new one which is still eroding away its floodplain.
Question: How far has the riverbed dropped?
Calculate your answer by doing the following:
Estimate the height of Saddlehorn Hill.
What’s the elevation where you are standing?
Drive to the second waypoint and figure out the elevation of the current riverbed by taking an elevation reading and then subtracting 25 feet since the river is below the middle of the bridge in front of you--don't walk out on the bridge or stop in the middle of it.
Subtract that number from the elevation of the first waypoint, then add the result to your estimate of the height of the hill for the answer.
Third task: It's strictly optional, but it would be great if you would post a picture of yourself and/or your GPSer in front of either the old or the new riverbed.
Please send me your answers to the questions above within 5 days of logging your find, or else per EarthCache rules, I will have to delete your log.
Thanks for visiting my EarthCache! I hope you enjoyed it, and I look forward to hearing from you!
***** Congratulations to jaylous1 on FTF!!! *****