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John Hopkins Glacier EarthCache

Hidden : 09/22/2011
Difficulty:
5 out of 5
Terrain:
3.5 out of 5

Size: Size:   other (other)

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Geocache Description:

To get credit for this Earth Cache you will need to answer the following questions.
1 Who named this Glacier and in what year and what did they name it after?
2 What is your estimate of the width of the glacial valley closest to you.
3 What is the length and height of this Glacier.
4 Time and date and name of how you got to the Glacier.
5 What type of Glacier is this?
6 What were the weather conditions while you were visiting this Glacier.

Glaciers are categorized in many ways including by their morphology, thermal characteristics or their behavior. Alpine glaciers form on the crests and slopes of mountains and are also known as "mountain glaciers", "niche glaciers", or "cirque glaciers". An alpine glacier that fills a valley is sometimes called a valley glacier. Larger glaciers that cover an entire mountain, mountain range, or volcano are known as an ice cap or ice field, such as the Juneau Icefield. Ice caps feed outlet glaciers, tongues of ice that extend into valleys below far from the margins of the larger ice masses.

The largest glacial bodies, ice sheets or continental glaciers, cover more than 50,000 km² (20,000 mile²). Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from the surface. The only extant ice sheets are the two that cover most of Antarctica and Greenland. These regions contain vast quantities of fresh water. The volume of ice is so large that if the Greenland ice sheet melted, it would cause sea levels to rise six meters (20 ft) all around the world. If the Antarctic ice sheet melted, sea levels would rise up to 65 meters (210 ft). Ice shelves are areas of floating ice, commonly located at the margin of an ice sheet. As a result they are thinner and have limited slopes and reduced velocities. Ice streams are fast-moving sections of an ice sheet. They can be several hundred kilometers long. Ice streams have narrow margins and on either side ice flow is usually an order of magnitude less. In Antarctica, many ice streams drain into large ice shelves. However, some drain directly into the sea, often with an ice tongue, like Mertz Glacier. In Greenland and Antarctica ice streams ending at the sea are often referred to as tidewater glaciers or outlet glaciers, such as Jakobshavn Isbræ.

Tidewater glaciers are glaciers that terminate in the sea. As the ice reaches the sea pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep, glaciers can calve underwater, causing the iceberg to suddenly leap up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over 10 km (6 mi) long. Yakutat Bay and Glacier Bay are both popular with cruise ship passengers because of the huge glaciers descending hundreds of feet to the water. This glacier type undergoes centuries-long cycles of advance and retreat that are much less affected by the climate changes currently causing the retreat of most other glaciers. Most tidewater glaciers are outlet glaciers of ice caps and ice fields.

In terms of thermal characteristics, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier has both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier.

Glacier formation.
Glaciers form where the accumulation of snow and ice exceeds ablation. As the snow and ice thicken, they reach a point where they begin to move, due to a combination of the surface slope and the pressure of the overlying snow and ice. On steeper slopes this can occur with as little as 15 m (50 ft) of snow-ice. The snow which forms temperate glaciers is subject to repeated freezing and thawing, which changes it into a form of granular ice called firn. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser and denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice has a slightly reduced density from ice formed from the direct freezing of water. The air between snowflakes becomes trapped and creates air bubbles between the ice crystals.

The distinctive blue tint of glacial ice is often wrongly attributed to Rayleigh scattering due to bubbles in the ice. The blue color is actually created for the same reason that water is blue, that is, its slight absorption of red light due to an overtone of the infrared OH stretching mode of the

The Johns Hopkins Glacier rises from the Fairweather Range on the east slopes of Lituya Mountain and Mount Salisbury and has a westerly flow towards the head of Johns Hopkins Inlet, 1 mile (1.6 km) southwest of the terminus of Clark Glacier and 79 miles (127 km) northwest of Hoonah. Its rock, ice and snow depict a variety of impressive colors such as grey, blue and white. It was named in 1893 by H.F. Reid after the Johns Hopkins University in Baltimore, Maryland, which sponsored an expedition to this glacier. It is the only advancing tidewater glacier now (its advance started in 1924 when Grand Pacific Glacier started receding towards Tarr Inlet) and is combined with Gilman Glacier (first got attached to Hopkins in the 1990s, broke off and rejoined several times and once again it appears joined since 2000); both are advancing as one single ice block, and at the waterfront, has a width of 1 mile (1.6 km) with a depth of 250 feet (76 m), rises to a height of 250 feet (76 m) and stretches to about 12 miles (19 km) upstream. Submarine calving has also been recorded.

The Johns Hopkins Glacier, for example, cannot be approached any nearer than about 2 miles (3.2 km) by sea because of the volume of the ice blocks that break loose from its cliffs. Most visitors to the park come by cruise ship and thus view the glaciers from the water

Much of this information was found on Wikipedia the rest you will have to be at GZ for the information.

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