The Eruptive History of Mt Hood

While historical accounts allow us to peek into the past to learn more about the past 1500 years of Mt Hood’s volcanic activity. But beyond that period, scientists have used geological surveys, core samples, and other scientific practices and theories to determine some of the details of previous eruptive periods.

During the middle of the 1800’s, Mt Hood went through a brief period of minor eruptions, producing little more than steam and ash from the small explosions.

Approximately 200 years ago, there was a more active period that produced pyroclastic flows, tephra falls, and lahars that flowed through the west and south valleys, and created the lava dome at Crater Rock.

About 1500 years ago, there was a much more substantial eruption, creating an avalanche of debris to flow from the upper-south flank, and created a lava dome near Crater Rock. The activity produced pyroclastic flows and lahars in the south and west valleys, as well as large tephra falls.

Prior to this, Mt Hood is said to have undergone the “growth period”, during which there were many explosions that produced the large lava dome, lava flows that created the lower flanks of the mountain, tephra falls and lahars that swept through the valleys below. The period is estimated to have been approximately 15,000 to 30,000 years ago, according to scientific studies.