SoonerStormchaser
5/22/2008, 06:52 AM
With Homey still MIA, I'll fill in again today, and tomorrow if necessary...but since I'm off to Ohio with the Mrs. on Saturday, if he's still not back, there won't be a GM thread.
May 22, 1915: Lassen Peak in California goes BOOM!
http://upload.wikimedia.org/wikipedia/commons/8/89/Lassen-Peak-Large.jpg
Lassen Peak (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from northern California to southwestern British Columbia. Located in the Shasta Cascade region of Northern California, Lassen rises 2,000 feet (610 m) above the surrounding terrain and has a volume of half a cubic mile, making it one of the largest lava domes on Earth.
Lassen Peak has the distinction of being the only volcano in the Cascades other than Mount St. Helens to erupt during the 20th century. On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash as far away as 200 miles (320 km) to the east. This explosion was the most powerful in a 1914–17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mount St. Helens in Washington. Lassen Volcanic National Park was created in Shasta County, California to preserve the devastated area and nearby volcanic wonders.
Unlike most lava domes, Lassen is topped by craters. In fact, a series of these craters exist around Lassen's summit, although two of these are now covered by solidified lava and sulfur deposits. Lassen is the largest of a group of more than 30 volcanic domes that have erupted over the past 300,000 years in the Lassen Volcanic Center.
http://upload.wikimedia.org/wikipedia/commons/8/8a/Lassen_Peak_Before_1914.jpg
On May 30, 1914, Lassen became active again after 27,000 years dormancy when it was shaken by a steam explosion. By mid-May 1915, more than 180 steam explosions had blasted out a 1,000 ft (300 m) wide crater near the summit of Lassen Peak.
On the evening of May 14, 1915, incandescent blocks of lava could be seen bouncing down the flanks of Lassen from as far away as the town of Manton, California 20 miles (30 km) to the west. By the next morning, a growing dome of lava had filled the volcano’s crater.
http://upload.wikimedia.org/wikipedia/commons/6/64/May_1915_Lassen_eruption_column.jpg
Then at 4:30 p.m. on May 22, after two quiet days, Lassen exploded in a powerful eruption (referred to as "the Great Explosion") that blasted volcanic ash, rock fragments and pumice high into the air. This created the larger and deeper of the two craters seen near the summit of the volcano today. A huge column of volcanic ash and gas rose more than 30,000 feet into the air and was visible from as far away as Eureka, California 150 miles to the west.
Pumice falling onto the northeastern slope of Lassen Peak generated a high-speed avalanche of hot ash, pumice, rock fragments, and gas, called a pyroclastic flow, that swept down the side of the volcano, devastating a 3 square miles area. The pyroclastic flow rapidly incorporated and melted snow in its path. The water from the melted snow transformed the flow into a highly fluid lahar that followed the path of the May 19–20 lahar and rushed nearly 10 miles down Lost Creek to Old Station. This new lahar released a large volume of water that flooded lower Hat Creek Valley.
The powerful climactic eruption of May 22 also swept away the northeast lobe of the lava flow extruded two days earlier. The eruption produced smaller mudflows on all flanks of Lassen Peak, deposited a layer of volcanic ash and pumice traceable for 25 miles to the northeast, and rained fine ash at least as far away as Winnemucca, Nevada, 200 miles to the east. Together these events created the Devastated Area which is still sparsely populated by trees due to the low nutrient and high porosity of the soil there.
http://upload.wikimedia.org/wikipedia/commons/d/d8/Lassen_Peak_in_June_1915.jpg
For several years after the May 22, 1915, eruption, spring snowmelt percolating down into Mount Lassen triggered steam explosions, an indication that rocks beneath the volcano’s surface remained hot. Particularly vigorous steam explosions in May 1917 blasted out the second of the two craters now seen near the northwest corner of the volcano’s summit (two older craters are buried).
May 22, 1915: Lassen Peak in California goes BOOM!
http://upload.wikimedia.org/wikipedia/commons/8/89/Lassen-Peak-Large.jpg
Lassen Peak (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from northern California to southwestern British Columbia. Located in the Shasta Cascade region of Northern California, Lassen rises 2,000 feet (610 m) above the surrounding terrain and has a volume of half a cubic mile, making it one of the largest lava domes on Earth.
Lassen Peak has the distinction of being the only volcano in the Cascades other than Mount St. Helens to erupt during the 20th century. On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash as far away as 200 miles (320 km) to the east. This explosion was the most powerful in a 1914–17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mount St. Helens in Washington. Lassen Volcanic National Park was created in Shasta County, California to preserve the devastated area and nearby volcanic wonders.
Unlike most lava domes, Lassen is topped by craters. In fact, a series of these craters exist around Lassen's summit, although two of these are now covered by solidified lava and sulfur deposits. Lassen is the largest of a group of more than 30 volcanic domes that have erupted over the past 300,000 years in the Lassen Volcanic Center.
http://upload.wikimedia.org/wikipedia/commons/8/8a/Lassen_Peak_Before_1914.jpg
On May 30, 1914, Lassen became active again after 27,000 years dormancy when it was shaken by a steam explosion. By mid-May 1915, more than 180 steam explosions had blasted out a 1,000 ft (300 m) wide crater near the summit of Lassen Peak.
On the evening of May 14, 1915, incandescent blocks of lava could be seen bouncing down the flanks of Lassen from as far away as the town of Manton, California 20 miles (30 km) to the west. By the next morning, a growing dome of lava had filled the volcano’s crater.
http://upload.wikimedia.org/wikipedia/commons/6/64/May_1915_Lassen_eruption_column.jpg
Then at 4:30 p.m. on May 22, after two quiet days, Lassen exploded in a powerful eruption (referred to as "the Great Explosion") that blasted volcanic ash, rock fragments and pumice high into the air. This created the larger and deeper of the two craters seen near the summit of the volcano today. A huge column of volcanic ash and gas rose more than 30,000 feet into the air and was visible from as far away as Eureka, California 150 miles to the west.
Pumice falling onto the northeastern slope of Lassen Peak generated a high-speed avalanche of hot ash, pumice, rock fragments, and gas, called a pyroclastic flow, that swept down the side of the volcano, devastating a 3 square miles area. The pyroclastic flow rapidly incorporated and melted snow in its path. The water from the melted snow transformed the flow into a highly fluid lahar that followed the path of the May 19–20 lahar and rushed nearly 10 miles down Lost Creek to Old Station. This new lahar released a large volume of water that flooded lower Hat Creek Valley.
The powerful climactic eruption of May 22 also swept away the northeast lobe of the lava flow extruded two days earlier. The eruption produced smaller mudflows on all flanks of Lassen Peak, deposited a layer of volcanic ash and pumice traceable for 25 miles to the northeast, and rained fine ash at least as far away as Winnemucca, Nevada, 200 miles to the east. Together these events created the Devastated Area which is still sparsely populated by trees due to the low nutrient and high porosity of the soil there.
http://upload.wikimedia.org/wikipedia/commons/d/d8/Lassen_Peak_in_June_1915.jpg
For several years after the May 22, 1915, eruption, spring snowmelt percolating down into Mount Lassen triggered steam explosions, an indication that rocks beneath the volcano’s surface remained hot. Particularly vigorous steam explosions in May 1917 blasted out the second of the two craters now seen near the northwest corner of the volcano’s summit (two older craters are buried).