Amon Basin Earthcache
In Washington, United States
Size:  (not chosen)
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*****This is an Earthcache. Please note the special requirements at the end of the cache description in order to log this cache as a find. You need to email me the answers to the questions below then log your find. Posting a picture is encouraged but optional.*****
You are currently at the Amon Creek Natural Preserve in the Amon Basin. The Tapteal Greenway Association has been actively working to preserve this area and has established trails in the area so feel free to follow them to further explore the area.
The Amon Basin is a watershed that drains a large part of the Badger Canyon area. Water collects in two forks which join together to form Amon Creek. The creek then empties into the Yakima River Delta near Bateman Island.
Each stream or river has a specific area of land that it drains, called a drainage basin (also called a watershed). The area of a drainage basin is defined by its underlying geological structure and slopes from higher ground toward lower areas. Runoff from springs, snowmelt, and rain flows out of the basin at its lowest point, and this is how a river or stream gets its water.
Believe it or not there was a much larger body of water flowing through Amon Basin at one time. This body of water is known today as the Yakima River.
About 9 million years ago the Columbia River flowed south from Vantage, across where the Hanford Nuclear Site currently lies. The river then turned west following the course of the present-day Yakima River, but upstream in reverse, as it made its way west toward to ocean.
Around 8 million years ago the landscape started growing into what are many of the today’s ridges and mountain ranges that we see today. Aside from the Cascade Mountains as a barrier, running through the Amon Basin is a series of hills that include Rattlesnake, Red, Candy, and Badger Mountains (as seen to the west). These hills are part of a major feature that geologists call the Olympic-Wallowa Lineament (OWL), which extends across the entire state of Washington beginning around Port Angles to northern Oregon. These changes to the landscape became significant barriers to the west-flowing Columbia River.
As a result of the barriers, the Columbia River changed its course to take the path of least resistance and began to flow through the Wallula Gap about 22 miles to the southeast of this location.
As a result of the Columbia River making its change to flow through the Wallula Gap, the Yakima River was formed and it began to flow east from the Cascade Mountains. The Yakima River originally turned south at Benton City and flowed a course through the Amon Basin, where Badger Canyon Road lies today.
Why doesn’t the Yakima River still flow here? The main geologic features that you now see in Amon Basin are part of the reason the river no longer flows there. It took the mighty Missoula Ice Age Floods, which occurred over 12,000 years ago, to re-route the Yakima River to its present-day course. As the torrential flood waters bottle-necked at Wallula Gap the flood waters slowed down and pooled, dropping their loads of gravel, sand and silt in the Amon Basin. The youngest Missoula flood sediment, which is about 10,000 years old, covers most of the Amon Basin.
As a result of these gravel deposits blocking the path of the Yakima River, it cut a course right between Rattlesnake Mountain and Red Mountain, spelling the end to the old Yakima River channel, and the birth of the present Yakima River channel.
Badger Canyon is filled with gravel dropped by one or more of the Missoula floods. Although the gravel deposits have since been covered up by silts and sands, you can see them where they are currently being mined in the south part of Richland (off of Steptoe Street) and the west end of Badger Canyon at Benton City.
To log this cache you must email me the answers to the following questions. Please do not post your answers in your log as these will be removed.
1. What type of of basin is Amon Basin?
2. What large body of water used to flow through Amon Basin?
3. What major event occurred that caused the large body of water to no longer flow through the area today and what did it leave behind to cause this change?
4. The sediment that covers much of the area is about how many years old?
5. Describe the ground composition where these coordinates take you.
Not a requirement, but feel free to post a picture of wildlife or the view from the Earthcache location.
Bjornstad, Bruce, 2006, On the Trail of the Ice Age Floods: A Geological Field Guide to the Mid-Columbia Basin, Keokee Co. Publishing, Inc., Sandpoint, Idaho.
Northwest Geology by Stephen Reidel.
Ice Age Floods Institute - www.iafi.org
(No hints available.)
Last Updated: on 10/12/2014 8:22:26 PM Pacific Daylight Time (3:22 AM GMT)
Coordinates are in the WGS84 datum