At the posted coordinates you will find an information sign that has some of the answers to the questions below. To obtain some answers you will need to read through the earthcache description and observe your surroundings.
To get to the cache's posted coordinates by the lake shore you have to use the trail that borders the lake. Please access the trail only through the trailhead posted coordinates or any other trailhead. If you try to reach the earthcache coordinates through any other access point you will trespass private property. We provided the closest access point to the trail that will take you to the information sign.
To log this cache successfully you need to visit the posted coordinates and answer the following questions:
1. How thick was the ice of sheet that shaped this valley?
2. Can you estimate the weight of the ice per square foot?
Hint: A cubic foot of ice weighs 57.2 pounds.
3. How long ago was this valley shaped?
4. Estimate how far in miles is the opposite shore of the lake?
5. What type of moraines can you identify on Lake Quinault? Briefly explain why do you think Lake Quinault presents that type of moraines?
6. What type of moraine acted as a natural dam trapping the melting water left behind when the ice retreated?
7. What direction from and to do you think the ice sheet flowed when it carved the lake bed of Lake Quinault’s thousands of years ago?
8. What mountain peaks and mountains ridge can you identify on the north side of Lake Quinault from the information sign at the earthcache posted coordinates?
The Shaping of the Quinault Valley
Probably the first thing that catches your attention when approaching Quinault is the majestic lake that lies at the bottom of the valley. The pristine waters of Lake Quinault are simply enchanting. This lake was carved thousands of years ago by a massive glacier that slowly flowed down shaping the entire Quinault Valley.
In the Quinault River Valley at least two major glacial advances occurred during the Late Pleistocene, the Humptulips and Chow Chow glaciations respectively. The Humptulips glacier was the most extensive. It advanced to within 4 km of the Pacific Ocean leaving behind broad moraines. After the interglacial period, ice again advanced to within 12 km of the Pacific Ocean during the Chow Chow glaciation where it constructed broad moraines. As the glacier retreated, it either re-advanced or stagnated constructing the moraines that dammed the river and began filling the lake bed left behind.
Presently, Quinault Lake forms a base level at an elevation of 57 meters above average sea-level. The lake has an average surface area of 1510 hectares and is one of the largest natural lakes on the Olympic Peninsula.
How Ice Sheets Form
Ice sheets formed like other glaciers. Snow accumulates year after year, then melts. The slightly melted snow gets harder and compresses. It slowly changes texture from fluffy powder to a block of hard, round ice pellets. New snow falls and buries the grainy snow. The hard snow underneath gets even denser and becomes firn.
Firn is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice. Firn has the appearance of wet sugar, but has a hardness that makes it extremely resistant to shovelling.
As years go by, layers of firn build on top of each other. When the ice grows thick enough—about 50 meters (165 feet)—the firn grains fuse into a huge mass of solid ice. At this point, the glacier begins to move under its own weight getting pull down by gravity.
Ice sheets tend to be slightly dome-shaped and spread out from their center. They behave plastically, or like a liquid. An ice sheet flows, oozes, and slides over uneven surfaces until it covers everything in its path, including entire valleys, mountains, and plains.
Compression and geothermal energy sometimes cause the bottom of an ice sheet to be slightly warmer than the ice above it. The bottom of the ice sheet melts, causing the ice above it to move at a faster rate than the rest of the ice sheet. These fast-moving glaciers are called ice streams.
Ice streams can move as quickly as 1,000 meters (.6 mile) every year. The slightly warmer, softer ice of the ice stream is where most of the ice sheet's crevasses are located. As a glacier carves its way through a landscape, it transports debris—mostly rock and soil. Moraine is the material left behind by a moving glacier.
The Quinault Lake Moraines
A moraine is material left behind by a moving glacier. This material is usually soil and rock. Just as rivers carry along all sorts of debris and silt that eventually builds up to form deltas, glaciers transport all sorts of dirt and boulders that build up to form moraines.
Moraines only show up in places that have, or used to have, glaciers. Glaciers shape the landscape in a process called glaciation. Glaciation can affect the land, rocks, and water in an area for thousands of years. That is why moraines are often very old.
Moraines are divided into five main categories: lateral moraines, medial moraines, supraglacial moraines, ground moraines and terminal moraines.
Lateral Moraine
A lateral moraine forms along the sides of a glacier. As the glacier scrapes along, it tears off rock and soil from both sides of its path. This material is deposited as lateral moraine at the top of the glacier’s edges. Lateral moraines are usually found in matching ridges on either side of the glacier. The glacier pushes material up the sides of the valley at about the same time, so lateral moraines usually have similar heights.
If a glacier melts, the lateral moraine will often remain as the high rims of a valley.
Medial Moraine
A medial moraine is found on top of and inside an existing glacier. Medial moraines are formed when two glaciers meet. Two lateral moraines from the different glaciers are pushed together. This material forms one line of rocks and dirt in the middle of the new, bigger glacier.
If a glacier melts, the medial moraine it leaves behind will be a long ridge of earth in the middle of a valley.
Supraglacial Moraine.
A supraglacial moraine is material on the surface of a glacier. Lateral and medial moraines can be supraglacial moraines. Supraglacial moraines are made up of rocks and earth that have fallen on the glacier from the surrounding landscape. Dust and dirt left by wind and rain become part of supraglacial moraines. Sometimes the supraglacial moraine is so heavy, it blocks the view of the ice river underneath.
If a glacier melts, supraglacial moraine is evenly distributed across a valley.
Ground Moraine
Ground moraines often show up as rolling, strangely shaped land covered in grass or other vegetation. They don’t have the sharp ridges of other moraines. A ground moraine is made of sediment that slowly builds up directly underneath a glacier by tiny streams, or as the result of a glacier meeting hills and valleys in the natural landscape. When a glacier melts, the ground moraine underneath is exposed.
Ground moraines are the most common type of moraine and can be found on every continent.
Terminal Moraine
A terminal moraine is also sometimes called an end moraine. It forms at the very end of a glacier, telling scientists today important information about the glacier and how it moved. At a terminal moraine, all the debris that was scooped up and pushed to the front of the glacier is deposited as a large clump of rocks, soil, and sediment.
Scientists study terminal moraines to see where the glacier flowed and how quickly it moved. Different rocks and minerals are located in specific places in the glacier’s path. If a mineral that is unique to one part of a landscape is present in a terminal moraine, geologists know the glacier must have flowed through that area.
This earthcache location has the permission of the Recreation and Trails Department of the Olympic National Forest, Hood Canal Ranger District.