Mount Hood

While not directly in Portland, Mount Hood sits about 50 miles east-southeast of Portland and could potentially affect Portland should it erupt. (Although ramifications such as lava flows or lahars would not directly affect the city, water supplies and transportation could be disturbed).

The City of Roses can rest in peace however knowing that the last major eruption of Mount Hood’s occurred before two gentlemen by the name of Lewis and Clark took their little trip to the Pacific Northwest. And despite minor activity in the mid 1800s, the volcano has remained relatively quiet since then.

This period of Hood’s tranquility is impressive when noting that it is more than 500,000 years old. Instead of volcanic temper tantrums, Hood has produced lava flows that travel no more than 6 to 8 miles from their starting point, that have created the flanks of the volcano one part at a time. At times, in opposition to flowing downhill at a tortoise like pace, the lava will pile up over the vent and create a lava dome that reaches hundreds of feet high.

These growing lava domes have continually disintegrated to form pyroclastic flows that have characteristics of quick movements and extremely hot temperatures. And even though very few of these flows have traveled more than around 8 miles, because they are extremely hot they have the ability to melt mass amounts of ice and snow, producing laharas that trickle down the river valleys that are typically far beyond the volcano’s flanks.

The growth and collapse of lava domes as well as the generation of lahars over the past 30,000 years have been the dominating factors of Mount Hood’s activity of eruption.

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Lava Flows: Flows that move downslope, away from the vent of a volcano burying or burning everything in their way. They form when lava piles up over a vent.

Lava dome: Lava piling up over a vent causes this formation.

Pyroclastic Flows: Avalanches of gas, ash and hot rock (up to 1500 degrees Fahrenheit) that are high speed (moving up to 100 mph) that are formed by the collapse of eruption columns or lava domes.

Lahars: Slurries of rocks, water and mud that move down river valleys at a fast pace. They have the ability to move, bury, and even smash objects in their path.

Mount Tabor

This dormant volcanic vent was given its name by Plympton Kelly, the son of Clinton Kelly. (Clinton was an Oregon City pioneer resident.) The name is in reference to Mount Tabor located in Israel.

The peak of Tabor reaches 636 feet in elevation and roughly 2/3 of this peak is a prominence that reaches about 200 feet in elevation.

The Tabor cinder cone is included in the Boring Lava Field.

Tabor is an extinct volcano, making Portland one of only four cities in the Unites States to house an extinct volcano.

Mount Tabor’s volcanic nature came into knowledge in 1912—which is years after it had been created into a park.

By the year 1900 the growing eastside population of Portland started to demand park space. Because of this in 1903, John C. Olmsted (landscaping architect) made the recommendation for the city to obtain more of the land at Mount Tabor. Six years later in 1909, forty lots of Mt. Tabor were purchased.

A naturalistic design for the park was created, including lengthy flights of stairs, copious amounts of walking trails and even a nursery yard. The plan also included native plants and the discovery of the volcanic cinders in 1912 was also utilized in the surfacing of the roads of the park.

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Dormant: Inactive as if in sleep.

Volcanic Vent: An opening in the crust of the earth where molten lava, ash and even gases are released.

Cinder Cone: A hill of steep nature that consists of glassy volcanic fragments that gather around and downwind from the volcanic vent. Sizes range from tens to even hundreds of meters in height.

Boring Lava Field: an extinct volcanic field zone that contains at the very least 32 small shield as well as cinder cone volcanoes that are lying within 12 miles of Kelly Butte and is located about 4 miles east of downtown Portland.