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What do Juneau about Glaciers?

A cache by merrittsbadges Send Message to Owner Message this owner
Hidden : 07/31/2008
Difficulty:
2 out of 5
Terrain:
2.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

Located just shy of the peak of Mt. Roberts with moderate to steep terrain reaching elevations near 3800 feet. The trail is well maintained hard pack, making access to the cache easy for the novice or experienced hiker. An easy hike from the tram.

The posted coordinates can be accessed by riding the Mount Roberts Tram for $25 and taking the shorter hike up Mt. Roberts Trail. Or hike the entire 4.5 mile (one way) Mount Roberts Trail. The trail is accessible at the end of 6th Street, downtown Juneau. You are looking for an information sign on the trail named “A Land Shaped by Ice”. There is no need to leave the trail to get credit for this cache.

Located just shy of the peak of Mt. Roberts, the cache offers a terrific view of Gastineau Channel and exhibits several geologic features common to areas influenced by glacial activity. The posted coordinates put you in an area which was covered by ice some 20,000 years ago. These glaciers cut through mountains moved rock, and compressed the land under their massive weight. Nearly every part of the natural history of Southeast Alaska, from surface geology to plant ecology, and the history of human and animal habitation were shaped by glacial forces.

Gastineau Channel, the most prominent feature from this vista, was once much deeper. The channel has been filled with thousands of years of glacial sediment. Mendenhall Glacier continues to deposit its sediment, taking material plucked from the mountains and depositing the material via meltwater into the channel. Even though the channel is narrow and shallow, it provides vital habitat as a rich estuary serving migratory birds. It also acts as a nursery providing sanctuary for young salmon, crab, and a host of other marine creatures.

If you examine the peaks around you, take note of which peaks are rounded and which exhibit a sharp “horn” peak. Massive sheets of glacial ice acted like sand paper, eroding the peaks below smoothing and rounding their appearance. Those peaks above the ice remain sharp in appearance, having eluded the glacial force.

Unlike the distinct “V” shaped erosion common with streams and rivers, glacial valleys exhibit a “U” shape, with a broad, flat base, and steep walls. Gold Creek Valley to the right, the numerous rounded valleys on Douglas Island, and of course Gastineau Channel, are all wonderful examples of the forces of glacial erosion.


To get credit for the cache, post a picture of yourself with Gastineau Channel in the background. If you are alone, post a picture of the information station named "A Land Shaped by Ice" at the posted coordinates with the channel in the background. I don't need to see the text on the sign, so a wider angle will be appreciated.

AND...Email me the following answers from the information station...

1. Name the Ice Age of 20,000 years ago?

2. What two factors will cause Douglas Island to be an island no more?

3. Has the land risen or fallen since the Ice Age and why?

4. Using the information on the board in paragraph titled "Glaciated Peaks", estimate the thickness of the Wisconsin Ice.

5. Why is Gastineau Channel technically a fjord?

Additional Hints (No hints available.)



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