Mount Shasta: A Volcano 500,000 Years in the Making - Mt. Shasta VP - California - Signs of History on Waymarking.com

One of a group of five Caltrans signs at the Mt. Shasta Vista Point on U.S. Hwy. 97. Geologic history sign about several topics including the eruptive episodes of the volcano. Text of Sign:

Volcanos Surround You!
Standing at this vista point, you can see four volcanos. Of these four, two different types of volcanos are present. With its steep conical sides, Mount Shasta is a great example of a “Stratovolcano”. This type of volcano forms, erupts, and then rebuilds itself in cycles. Eruptions are often quite violent and eject massive amounts of gas, ash, and rock. Deer Mountain (left), Whaleback Mountain (front), and Herd Peak (behind you) are “Shield” volcanos. Notice how they are a different shape? Low and broad, this type of volcano is formed by the buildup of solidified slow-moving molten lava flows and smaller cinder cone eruptions.
Look to Sheep Rock (right) for a remnant of ancient times. While not a volcano itself, Sheep Rock is made up of volcanic rubble and ash ejected from a nearby volcano about 30 million years ago.

Mount Shasta: A Jewel in the “Ring of Fire”
The “Ring of Fire” circles the Pacific Ocean, releasing heat and pressure from the Earth’s interior to create volcanos and frequent earthquakes.
Mount Shasta is the largest volcano of the Cascade Range. It is a part of the Ring of Fire between British Columbia and Lassen Peak.

Mount Shasta’s Eruptive Episodes
Mount Shasta evolved through five major stages, spanning about 500,000 years.
The first stage volcano grew as large as the mountain before you, but was largely destroyed in a huge volcanic eruption and avalanche 300,000 years ago.
Mount Shasta rebuilt itself during four more eruptive stages. Layers of molten lava flows cooled and hardened, overlapping each layer to form the mountain you see today. The Misery Hill, Shastina, and Hotlum volcanic cones, and the Military Pass lava flow, are evidence of these four stages.
Mount Shasta has erupted at least 10 times in the past 4,500 years, about once every few hundred years. Mount Shasta’s latest eruption may have been in 1786, as reportedly witnessed by the seafaring explorer Laperouse while sailing off the coast of northern California

Moving Glaciers!
Mount Shasta hosts California’s largest active glaciers.
From this viewpoint, most noticeable is the Hotlum Glacier, the large field of snow and ice below the summit on the left, and Bolam Glacier, further to the right.
Whitney Glacier is the biggest, but is somewhat hidden from this viewpoint within a deep cleft between Mount Shasta and Shastina.
Unlike most others on Earth, these glaciers have doubled in size since 1950. Today their future remains uncertain.

Group that erected the marker: Caltrans and Forest Service URL of a web site with more information about the history mentioned on the sign: [Web Link] Address of where the marker is located. Approximate if necessary: Mt. Shasta Vista Point U.S. Hwy. 97California United States

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Date Logged Log   11/03/2012 NW_history_buff visited it 09/22/2012 Volcanoguy visited it

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