This picture shows the debris covered "snout," or terminus, of Emmons Glacier on the east side of Mt. Rainier. Emmons Glacier is a valley glacier. The dark color of its terminus is due to avalanches of rock that have fallen on the glacial ice.

The stream that comes from the terminus of Emmons Glacier is the beginning of the White River, which flows into the Puget Sound lowlands. It is a braided stream, a network of multiple channels that fork and rejoin. Glacial meltwater streams are commonly braided, due to the excess of sediment that the glacier dumps into the stream system. This is in contrast with meandering streams that have a single channel, and are in a more steady balance with their supply of sediments.

The terminus of Emmons Glacier and its valley illustrate several points about glaciers in general and about Mt. Rainier and its glaciers in particular:

1. avalanches of rock are common from the unstable slopes of composite cone volcanoes like Mt. Rainier
2. braided streams are common where glaciers overload their meltwater streams with sediments
3. the retreat of valley glaciers on mountains of the Northwest during the last few centuries followed a larger retreat late in the Pleistocene epoch over 10,000 years BP, leaving behind glacially eroded valleys strewn with glacial drift
4. lahars, dangerous mudflows, are a constant threat from the slopes of composite cones like Mt. Rainier
5. eruptions of lava and tephra that build up a composite cone like Mt. Rainier are constantly attacked by erosion in the form of flowing glaciers, steeply plunging streams, landslides and lahars

Stevens Ridge Formation

This photo shows layers of lava (the rockier outcrops) and volcanic ash and tuff, on a ridge above the valley of the upper White River near Emmons Glacier. The layers of volcanic rock are part of the Stevens Ridge Formation, which is an older sequence of volcanic rocks that covered much of this region of the Cascade Range millions of years before Mt. Rainier started to form. The Stevens Ridge rocks erupted during the Oligocene and early Miocene epochs, approximately 25 to 20 Ma. Mt. Rainier did not start forming until approximately 500,000 years ago. During the intervening time, erosion cut deeply into the Stevens Ridge Formation, just as it is already starting to do to the rocks of Mt. Rainier. Select the image to see a larger view. Use your browser's back button to return to this page.

Avalanche Deposit on Till

This picture shows three types of unconsolidated sediments: (1) a debris avalanche deposit of rocks and boulders, (2) a glacial till, and (3) alluvium. Select the image to see a larger view. Use your browser's back button to return to this page.

The debris avalanche deposit is the remnant of a landslide of rock that tumbled down the slopes of Mt. Rainier onto the Emmons Glacier and the valley beneath the glacial terminus. It is marked by large, angular boulders, and covers much of the central area of the photograph.

The till is largely covered by the avalanche deposit, but at the base of the slope (bottom of the picture) till is visible. It is darker gray and does not have the abundant large, angular boulders of the avalanche deposit. Glacial till also forms the dark gray ridge along the far side of the lake. The avalanche of rock debris did not flow far enough to engulf the entire ridge of glacial till. You can see where the avalanche stopped flowing up the ridge of glacial till beside the lake - it is where the abundant large, angular boulders come to an end.

The ridge of glacial till on the far side of the lake is actually a terminal moraine. It was left from the last advance of the Emmons Glacier, which happened during the "Little Ice Age" between 1,000 years ago and 150 years ago. The lake formed after the glacier retreated - it is a moraine-impounded lake.

The lake is unstable. The terminal moraine that dams the lake is made of loose rock debris and contains chunks of glacial ice that are still melting. Because of its instability, the lake could break through the terminal moraine that dams it and create a small lahar rushing down the upper White River. Just below the lake, along the upper White River lies a campground that could be devastated if the lake burst through the moraine and created a lahar.

Lateral Moraine

This picture looks up the terminus of Emmons Glacier to Mt. Rainier. You can see the cleaner white ice of upper Emmons Glacier high on the slopes of the volcano. In the foreground, a braid of the upper White River drains from Emmons Glacier, reworking glacial till into alluvium. Select the image to see a larger view. Use your browser's back button to return to this page.

A lateral moraine appears on the right of the photo, above the light green shrubs and beneath the dark green fir trees. It was deposited alongside the glacier, when the flowing glacial ice extended farther down the valley and filled the valley up to the level of the lateral moraine. Given how the till looks fresh, with no sign of weathering and almost no vegetation, the lateral moraine probably formed during the Little Ice Age, at the same time as the terminal moraine that impounds the lake in the picture above.

Braided Stream

This picture shows the braided course of the upper White River flowing down from the terminus of the Emmons Glacier. The ridge in the far distance is made of older volcanic rocks of the Stevens Ridge Formation. The nearby valley wall on the right, where it is free of fir trees, show how far up the side of the valley the Emmons Glacier reached when it was at its Little Ice Age maximum, within the last 1,000 years. The White River is reworking the glacial till and debris avalanche deposit, sorting and re-depositing the sediments into alluvium. The erosion of Mt. Rainier continues. Select the image to see a larger view. Use your browser's back button to return to this page.

Glossary terms that appear on this page: valley glacier; braided stream; meandering stream; composite cone; glacial drift; lahar; tephra; lava; volcanic ash; tuff; debris avalanche; glacial till; alluvium; terminal moraine; lateral moraine