Hells Canyon: Land of Fire and Water EarthCache
Hidden : 10/8/2013
Difficulty:
3.5 out of 5
Terrain:
2 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

The coordinates lead you to the parking area for the Hells Canyon Overlook. Go for a short stroll to the overlook and see the beautiful view of Hells Canyon.

Hells Canyon is the deepest gorge in North America, averaging about 10 miles in width and a height of about a mile and a half. It is relatively YOUNG compared to the formation of the area: the canyon itself is only about 6 million years old. In comparison, the area here was shaped about 300 million years ago when an arc of volcanoes developed in what was then the Pacific Ocean. Over millions of years, the volcanoes subsided and rock built up on the underwater plates. Between 130 and 17 million years ago, two oceanic plates in the South Pacific converged violently, which changed the shape of this area significantly. Then, a period of volcanic activity followed and much of the area was covered with floods of basalt lava. This smoothed the topography into a high plateau about a mile thick over thousands of years. Significant canyon-shaping events via glacial activity and flooding occurred as recently as 15,000 years ago when a massive outburst flood came from Glacial Lake Bonneville in Utah. The Snake River likely only began carving the area out around 6,000 years ago - and it has been the biggest influence on carving the Hells Canyon you see in front of you today.

You can see some of this entire process in the bluffs around you. The large, flat, tan terraces you see are deposits from the Missoula Floods. These flood events happened because this whole area was covered with glaciers and massive glacial lakes. The darker gray below them - sometimes seen very clearly - were etched by deposits during the Bonneville Floods. When you are driving around the area, you can see more evidence of geological events like: giant current ripples (which appear in valleys like small rolling hills), flood bars (see Pittsburgh Landing), and layers of Mazama ash (prominent gray to white lines in the bluffs). You can even see many pictographs and petroglyphs all around the Hells Canyon area left by our ancestors from years ago.

To appreciate this geological process, walk along the trail to the overlook. Look out over the canyon and surrounding area. Hopefully by completing the tasks of this earth cache you will learn more about the processes that shaped this beautiful area. The geological story here is about opposites that work together: fire and water....of building up and wearing down.

To get credit for completing this earth cache and logging a find, you must submit the following answers to the cache owner via geocaching.com. Please do not post the answers in your log, or it will be deleted.
1. What are the four basic time periods involved in the geological time frame for Hells Canyon, and what process does each represent?
2. When the mountains in Central Idaho were forced up, what was displaced?
3. Look at the canyon before you. Think about the amount of Columbia River Basalt that poured out in this area: 70,000 square miles. If you were to parcel out that space into 1 acre lots for a family home, how many families would get a piece of land? Answer this: How does this shape what you think about the size of the geological event that created this area?
4. For more perspective, think about how deep you imagine [or know] the Grand Canyon to be compared to the canyon in front of you. The East Rim of Hells Canyon is 8,000 feet high, and the highest area of the Grand Canyon is the North Rise. Assuming that the river is the level for which to start for each, Answer: (a) which is deeper, and (b) by about how much?

Additional Hints (No hints available.)



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