These notes will help you fill out your Cispus Journal
(Click here for 2007 picts and click here to see the MSH Digital Story)

Click here to see the score we gave to Yellow Jacket Creek for page 16 on macroinvertebrates.

Ponds Hike Picts (to check your sketches, pgs 14 & 15)
Click here to see pictures of the Pond going back to 1999!

Click here to read about Harry Truman, the one who died in his lodge on Spirit Lake.

Click here to read about some of the 57 people who died on the 1980 eruption.

Click here to read about the photographers who got the amazing photos of the MSH blast and other photos (among others who died)!

Use the info here to complete p. 12 in your Cispus Journal.

On May 18, 1980 Mt Saint Helens erupted. Since Mt Saint Helens erupts with cinders and lava flows it is a composite volcano. The blast went sideways so it was a lateral blast. Mt Saint Helens is one of the several Cascade Range volcanoes.On May 18 an enormous column of ash thrust 15 miles into the sky. It continued to eject ash for about nine hours. The plume deposited ash and pumice downwind from the volcano. The ash was blown eastward by the wind at about 60 miles per hour. Some of the ash reached the eastern United States within 3 days. Small particles entered the jet stream and circled the Earth within two weeks.

There are many examples of life returning to Mt Saint Helens from the trees and plants that are all over the blast zone. Also in Meta Lake there are many trees as well as tadpoles, birds and fish. Deer are spotted at times, too.

Mt St Helens’ Mud Flows - As the ash column rose, the edges collapsed onto the slopes of the newly formed crater. This superheated ash quickly melted and mixed with existing snow and ice. Then it began to flow downslope. The water quickly picked up rock debris as it sped from the volcano. This debris included boulders as large as 20 feet in diameter. Mudflows can travel as fast as 30 miles an hour. They can easily rip trees, houses, and bridges from the ground. Mudflows sped from the volcano's west, south, and east sides within minutes of the eruption. The largest mudflow started on the debris-avalanche deposit about 4 hours later. Most of the water that poured across the surface of the debris avalanche deposit came from the deposit itself. This included water that had been trapped inside the volcano, and melting blocks of ice that had been glaciers on the volcano. The mudflow sloshed from side-to-side as it rushed through forests and clearcuts. It left its unmistakable mark on the land. From the toe of the deposit, millions of tons of debris broke loose and devastated downstream communities. Homes were carried away and deposited many miles downstream, or simply, destroyed by bridges. The mighty Columbia River was closed to freighter traffic for several days as the debris was dredged out.

Mount St. Helens erupted often between 1980 and 1986. An explosive eruption on March 19, 1982, sent pumice and ash 9 miles (14 kilometers) into the air, and resulted in a lahar flowing from the crater into the North Fork Toutle River valley. Part of the lahar entered Spirit Lake (lower left corner) but most of the flow went west down the Toutle River, eventually reaching the Cowlitz River, 50 miles (80 kilometers) downstream. A major problem to people living downstream of Mount St. Helens was the high sedimentation rates resulting from stream erosion of the volcanic deposits. Streams were continuously down cutting channels, eroding their banks, and eating away at the avalanche and lahar deposits. This material was eventually transported downstream and deposited on the streambeds, decreasing the carrying capacity of the channels and increasing the chances of floods. In order to remove the May 18, 1980 sediment deposits, and to keep up with new sedimentation, the U.S. Army Corps of Engineers began a dredging program on the Toutle, the Cowlitz, and the Columbia Rivers. By 1987, nearly 140 million cubic yards (110 million meters) of material had been removed from the channels. This is enough material to build twelve lanes of highway, one-foot thick, from New York to San Francisco.

Mt St Helens’ Lava Dome - Inside the giant horseshoe- shaped crater of Mount St. Helens, 17 eruptions between 1980 and 1991 have built a mound-shaped pile of lava called a lava dome. The dome is 3,450 feet wide and contains about 97 million cubic yards of lava. At its highest point from the crater floor, it is more than 1300 feet tall. That's taller than the Empire State Building. But as large as this may seem, the dome has only replaced about 4 percent of the volcano that was removed on May 18, 1980. Each new eruption adds lava to the dome. This was usually as an oval-shaped lava flow as thick as 100 feet and more than 1,000 feet across. Mt Saint Helens erupted again in 1986, then again in October of 2004. It has been erupting since 2004 and continues to erupt even now.

Spirit Lake - The debris avalanche that triggered the eruption slid north into Spirit Lake and west 25 kilometers down the North Fork Toutle River valley, covering the valley floor with unconsolidated debris to an average depth of 45 meters and as much as 180 meters in some places. The debris avalanche raised the level of Spirit Lake 64 meters and dammed its natural outlet even higher. Many small ponds filled closed depressions on top of the avalanche deposit, and several lakes formed in tributaries dammed by the avalanche.

Use the following for Johnston Ridge Observatory pages:
Here are the questions in case you don't have the Johnston Ridge Observatory packet -

Mount St. Helens: Blowing, Flowing and Glowing

Describe the lateral blasts impacts to the pre-eruption forest.

Why do you think the lateral blast able to kill trees on both sides of the ridges?

What are the mounds to the east of the Johnston ridge and how did they get there?

The ground in the lower half of the valley has a different color and texture than the ground on the upper half of the valley. What could account for the differences in color?

The landslide fell from the north side of the volcano, but traveled farther west than north. Why do you think this happened? Explain your answer.

Why are there so few hummocks between Johnston Ridge and volcano?

Did topography influence the movement of the landslide, lateral blast, and pyroclastic flows on May 18, 1980? What is your evidence?

Constructive Destruction

Explain why each eruptive event was destructive, constructive or both.

What type of volcano, shield or composite volcanoes, do you think are the most destructive?   Why?

Explain how the lava domes change the crater of Mount St. Helens.

Describe two eruptive processes visible on the crater walls that helped construct Mount St. Helens.

What two eruptive events at Mount St. Helens led to the discovery of similar events at other volcanoes? 

Describe what the on-going eruption has done to the crater glacier?

The current eruption and May 18, 1980 show ways Mount St. Helens builds and destroys itself.  What processes do you think will change Mount St. Helens in the next 500 years?  How do you think Mount St. Helens will look 500 years from now?

Biologic Pathways

The diameter of the stumps and logs indicates that the trees that stood here were between 150 to 250 feet tall.  Describe the 300 mph lateral blasts impacts to the forests that once grew here.

Why was the lateral blast able to kill trees on both sides of the ridges, and so far away?

Use the chart below to identify how environmental factors affect each slope differently.  (Use: ‘more’, ‘less’, ‘about the same’)

Which side of Johnston Ridge appears to have more plant life growing on it?
On which side of Johnston Ridge could plants and animals have survived?  Why?
Of the three factors listed in the chart above, which factor could have enabled plants or animals to survive the lateral blast?

Geologist David Johnston died on this ridge on May 18, 1980.  The animals listed in the table lived here before the eruption. Which animals could have survived the eruption at this site, and which colonized it afterward?

What could account for the lack of blown down trees and differences in color alongside the highway to the left of the Johnston Ridge?    

The creek located in this valley re-formed after the eruption.  How has the presence of water in the valley impacted the return of life?  Explain your answer.

If the landslide fell from the north side of the volcano, why did it travel much farther west than north? 

Prior to the eruption, 30 lakes and ponds existed within what is now the blast zone.  150 new lakes, ponds, and wetlands formed in the Toutle River Valley as a result of the landslide. How has the presence of water in the valley impacted the return of life?

The eruption began with a landslide that filled the Toutle Valley below to a depth of over 300 feet. Why are there so few hummocks in the valley between Johnston Ridge and volcano?

The deposits that buried the hummocks were 1,350 degrees Fahrenheight.  Could any plant or animal survive these temperatures?  If so how?

Large flood plains and canyons on the valley floor formed after the eruption.  How might these flood plains and canyons affect the return of plant and animal life?

The climate in the valley is harsh. Pumice rocks are filled with tiny holes that cause water to flow through the rock instead of being absorbed.  Pumice’s light color also reflects sunlight, creating hot surface temperatures.  How might these climatic conditions affect colonizing plants?  

You can find answers to the questions here:

Case Facts:

Vocabulary:

• Landslide:  a rapid and unusually sudden sliding or flowage of unsorted masses of rock and other material falling under the force of gravity
• Lateral Blast: a large explosion directed out of the side of a volcano containing a turbulent mixture of hot gas, ash, and rock that flow over the ground at high speeds under the influence of gravity.
• Pyroclastic Flow: the lateral flow of a turbulent mixture of hot gases and unsorted ash, pumice, and volcanic fragments that flow under the influence of gravity. {Pyro (fire) clastic (broken rock)}
• Hummock: large mounds of rock deposited by a landslide.
• Habitat: the native environment of a plant or animal.
• Ecosystem: a community of organisms and their interaction between each other and their environment.
• Abiotic:: of or related to the non-biological aspects of an ecosystem (i.e. water, rocks, sunlight, degree of slope)

The lateral blast shattered and splintered the forest that stood here. Tree trunks, branches, and bark were swept away.  Scientists believe the blast cloud doubled in volume the first five miles it raveled by shattering the forest in its pathway._

Plant communities beneath the trees were buried under rock and ash. The case facts reveal that the lateral blast was composed of hot gasses, ash, and rock. Rock made the blast cloud heavy, which held it close to the ground.  Gasses allowed the blast cloud to flow like a fluid up and over ridge tops. The mounds on the top of the ridge are hummocks, indicating the landslide spilled over Johnston Ridge then flowed down the South Coldwater Creek drainage. 

The landslide spilled over in two locations, separated by a small narrow patch of blown down trees. When the landslide spilled over Johnston Ridge, it turned and flowed down the South Coldwater Creek.  The lighter color in the lower half of the drainage is due to the landslide, which scoured away the soil exposing bedrock. A “trim line” reveals the height of the landslide as it flowed down South Coldwater Creek. The landslide fell from the north face of the volcano, but traveled 13.5 miles to the west because it struck Johnston Ridge.  When the landslide hit Johnston Ridge, it was deflected westward. 

The landslide scraped away the soil, exposing bedrock, as the landslide crashed against the ridge. There are few hummocks between Johnston Ridge and the volcano, because pyroclastic flows covered most of the landslide deposits within five miles of Mount St. Helens.  These super-heated rock avalanches began to spill out of the crater about 4-hours after the eruption began, covering the landslide deposit with up to 130 feet of ash and pumice. Blown down trees and shattered stumps reveal that topography influenced the direction the blast traveled. Hummocks and scour marks reveal that Johnston Ridge deflected and directed the landslide down the Toutle River valley, and down the South Coldwater Creek drainage.

Pyroclastic flows travel as far as slope and gravity allow. The presence of hummocks just down valley from Johnston Ridge indicates that the topography influenced how far the pyroclastic flows were able to move.

The landslide destroyed much of mountain--Ninety percent of what is now missing collapsed in the landslide. However,it also  filled the Toutle River Valley with hundreds of feet of rock, doubled the size of Spirit Lake, created Coldwater and Castle Lakes, and 150 new ponds and wetlands. The lateral blast erupted lava from Mount St. Helens.  This further destroyed the mountain and the surrounding forest.

Ash and pumice from the plume injured trees and buried plants and crops. Pumice creates well drained “soils” in a wet climate, and in time the ash will become nutrient rich. Mudflows destroyed fish habitat, houses, bridges, and clogged river valleys with debris.  However, the deposits also raised the valley bottoms. Pyroclastic flows raised the valley by covering the landslide with pumice and ash, but were also so hot that they killed all life forms directly in their pathway. The volcano rebuilds itself by creating new lava domes.

The entire chain of Hawaiian Islands is the result eruptions where layer after layer of thin fast-moving of Basalt lava.  However, these eruptions are also destructive. It takes decades for soils to form in areas impacted by these lava flows basaltic eruptions, which greatly slows the pace of recovery.   

Composite volcanoes can erupt with tremendous violence. The results of the May 18th eruption are impressive, but Mount St. Helens has experienced eruptions 16  times larger than the 1980 event.  Starting in 1980 more than a dozen lava eruptions built the dome. 

Each eruption squeezed a new layer of thick lava onto the existing dome. All of these layers built a lava dome that is more than 900 ft tall in the crater of Mount St. Helens. Hot acidic water changed the chemical composition of an old dome.  This makes it weak like clay and can change the rock’s color.  (This is called hydrothermal alteration.  The rock shown in the exhibit is white).

You can see pumice deposits in the crater walls from past eruptions. Silver and red layers are visible as evidence of old lava flows. The May 18, 1980 landslide and lateral blast enabled scientists to discover landslide deposits (hummocks) and horseshoe-shaped craters created by lateral blasts throughout the world.

The on-going eruption has melted about 20% of the glacial ice.  It has shoved the glacier against the crater walls.  This process thickened and tilted the glacier, causing it to flow rapidly out of the crater.  This is the fastest flowing and fastest growing glacier in the world. The 1980-86 dome, crater glacier and new dome have already changed the crater in amazing ways. The current eruption could stop tomorrow or continue for decades.

Mount St Helens often remains intermittently active for 50 to 100 years after a major eruption—a dome grew for 100 years after an eruption in 1480. However an explosive eruption will certainly occur in the future.  Over the past 4,000 years the volcano has awakened and erupted every 150 to 200 years.

The lateral blast shattered and splintered the forest that stood here. Tree trunks, branches, and bark were swept away.  The impacts significantly increased the volume of the blast cloud. Scientists believe the cloud doubled in volume the first five miles it raveled by shattering the forest in its pathway._

Plant communities beneath the trees were buried under rock and ash. The case facts reveal that the lateral blast was composed of hot gasses, ash, and rock. Rock made the blast cloud heavy, which held it close to the ground.  Gasses allowed the blast cloud to flow like a fluid up and over ridge tops.

The north side, because it offered some protection from the direct brunt of the lateral blast. Deep snow packs on north facing slopes protected some small plants and animals from the blasts intense heat.

The “case facts” indicate that the mounds are hummocks. Hummocks were deposited there when the landslide tumbled over Johnston Ridge.  The narrow patch of blown down trees in foreground of the mounds reveal that the landslide spilled over Johnston Ridge in two locations.

The “case facts” indicate that the absence of trees and exposed bedrock reveal areas scoured or buried by the landslide. As the landslide crested Johnston Ridge it turned and flowed down the South Coldwater Creek drainage. The scour marks in the valley reveal the height of the landslide as it flowed down the drainage. Sitka and red alder trees were able to colonize the creeks moist shorelines. 

These clearly visible alder forests are slowly spreading up the hillsides, accelerating the pace of recovery in the landslide-scoured areas and adjacent blown down forests. When the landslide hit Johnston Ridge, it scraped away the soil and exposed bedrock on the right side of the ridge facing the volcano. Although the landslide fell from the north side of the volcano, it was deflected westward by Johnston Ridge. 

As the landslide entered the Toutle River Valley it was funneled down slope and traveled 13.5 miles to the west. Most of the valley floor appears to be forested.  There is far more vegetation growing in the valley than on this ridge.  Water enabled trees (alder, willow, and cottonwood) to establish along the  moist shorelines of the new ponds and wetlands.  After gaining a foothold in these moist sites, the forests have spread across the valley floor and up the surrounding hillsides. 

This spreading process is clearly accelerating the pace of recovery on the landslide deposit and in the adjacent blown down forest. There are few hummocks between Johnston Ridge and the volcano, because they were covered by pyroclastic flows.  

These super-heated rock avalanches spilled out of the crater and covered most of the landslide deposit within five miles of the volcano with 130 feet of ash and pumice. No plants or animals survived the 1350 degree F deposits that buried the hummocks.

Plant seeds do not have time to take root before they are washed away when water levels are high. The absence of root systems allows sediment to continue to be washed away. The pumice plain is located within a very wet climate, but water is in short supply during the summer when plants need it most. 

These drought-like conditions and intense heat make it very difficult for plants to colonize this site.  Temperature measurements taken on the pumice plain during the month of August were eight degrees Celsius higher than temperatures taken in forests surrounding the blast zone. 

Plant communities reflect these harsh conditions. Many plants growing on the pumice plain are normally found at high elevation sites.  In a sense, the eruption “lowered timberline” at Mount St. Helens by creating a similar environment in the valley.

Each stage of the eruption changed the landscape in different ways thus the biologic recovery is different in each area.  Plants and animals survived the eruption on north facing slopes within areas impacted by the lateral blast. The legacy of these survivors is clearly visible on the north side of Johnston Ridge. 

Dense alder forests covered much of the areas impacted by the landslide.  The presence of water in the South Coldwater Creek drainage and the creation of new ponds and wetlands in the Toutle River Valley clearly reveal that water is fueling spectacular change. 

The intensity of the disturbance caused by the pyroclastic flows, lack of survivors, and harsh environment created have caused the pumice plain to recovery at a far slower pace.