USGS/Cascades Volcano Observatory
Vancouver, Washington

1. The Cascade Range is a volcanic chain stretching from northern California to British Columbia

2. The smallest of five major volcanic peaks in Washington State is Mount St. Helens, with an elevation of 9,677 feet (2,950 m) before the eruption of May 18,1980. Another Cascade volcano, Mt. Adams (12,286 ft [3,745 m]), is in the distance. The view is from the west.

(April 10, 1980 by Donald A. Swanson, USGS/CVO)

3. On March 20, 1980, after a quiet period of 123 years, earthquake activity once again began under Mount St. Helens volcano. Seven days later, on March 27, small phreatic (steam) explosions began. This view is from the northeast.

(April 10, 1980 by Donald A. Swanson, USGS/CVO)

4. A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 m) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 m). The view is from the northeast.

(April 27, 1980, by Peter W. Lipman, USGS)

5. On May 18, 1980, at 8:32 a.m. Pacific Daylight Time, a magnitude 5.1 earthquake shook Mount St. Helens. The bulge and surrounding area slid away in a gigantic rockslide and debris avalanche, releasing pressure, and triggering a major pumice and ash eruption of the volcano. Thirteen-hundred feet (400 m) of the peak collapsed or blew outwards. As a result, 24 square miles (62 square Km) of valley was filled by a debris avalanche, 250 square miles (650 square km) of recreation, timber, and private lands were damaged by a lateral blast, and an estimated 200 million cubic yards (150 million cubic meters) of material was deposited directly by lahars (volcanic mudflows) into the river channels. Fifty-seven people were killed or are still missing.

(May 18, 1980, by Austin Post, USGS)

6. For more than nine hours a vigorous plume of ash erupted, eventually reaching 12 to 15 miles (20-25 km) above sea level. The plume moved eastward at an average speed of 60 miles per hour (95 km/hr), with ash reaching Idaho by noon. By early May 19, the devastating eruption was over. Shown here is a close-up view of the May 18 ash plume.

(May 18, 1980, by Donald A. Swanson, USGS)

7. Map of the area around Mount St. Helens which were affected by the May 18, 1980 eruption. North is to the top.

8. After the May 18, 1980 eruption, Mount St. Helens' elevation was only 8364 feet (2,550 m) and the volcano had a one-mile-wide (1.5 km) horseshoe-shaped crater, seen here from the northwest.

(September 16, 1980, by Thomas J. Casadevall, USGS)

9. For weeks volcanic ash covered the landscape around the volcano and for several hundred miles downwind to the east. Noticeable ash fell in eleven states. The total volume of ash (before its compaction by rainfall) was approximately 0.26 cubic mile (1.01 cubic km), or enough ash to cover a football field to a depth of 150 miles (240 km). In this photograph, a helicopter stirs up ash while trying to land in the devastated area.

(August 22, 1980, by Lyn Topinka, USGS/CVO)

10. The slopes of Smith Creek valley, east of Mount St. Helens, show trees blown down by the lateral blast. Two U.S. Geological Survey scientists (lower right) give scale. The direction of the blast, shown here from left to right, is apparent in the alignment of the downed trees. Over four billion board feet of usable timber, enough to build 150,000 homes, was damaged or destroyed.

(September 24, 1980, by Lyn Topinka, USGS/CVO)

11. Spirit Lake, once surrounded by lush forest, is within the area devastated by blast. Remnants of the forest now float on the surface of the lake. Another Cascade volcano, Mt. Rainier (14,410 ft [4,392 m]), is in the distance. The view is from the south.

(October 4, 1980, by Lyn Topinka, USGS/CVO)

12. This downstream view of the North Fork Toutle River valley, north and west of St. Helens, shows part of the nearly 2/3 cubic miles (2.3 cubic km) of debris avalanche that slid from the volcano on May 18. This is enough material to cover Washington, D.C. to a depth of 14 feet (4 m). The avalanche traveled approximately 15 miles (24 km) downstream at a velocity exceeding 150 miles per hour (240 km/hr). It left behind a hummocky deposit with an average thickness of 150 feet (45 m) and a maximum thickness of 600 feet (180 m).

(November 30, 1983, by Lyn Topinka, USGS/CVO)

13. Nearly 135 miles (220 km) of river channels surrounding the volcano were affected by the lahars of May 18. A mudline left behind on trees shows depths reached by the mud. A scientist (middle right) gives scale. This view is along the Muddy River, southeast of Mount St. Helens.

(October 23,1980, by Lyn Topinka, USGS/CVO)

14. More than 200 homes and over 185 miles (300 km) of roads were destroyed by the 1980 lahars. Pictured here is a damaged home along the South Fork Toutle River.

(July 19, 1981, by Lyn Topinka, USGS/CVO)

15. During the May 18, 1980 eruption, at least 17 separate pyroclastic flows descended the flanks of Mount St. Helens. Pyroclastic flows typically move at speeds of over 60 miles per hour (100 km/hr) and reach temperatures of over 800 Degrees Farenheit (400 degrees celsius). Photographed here, a pyroclastic flow stretches from Mount St. Helens' crater to the valley floor below.

(August 7, 1980, by Peter W. Lipman, USGS)

16. A U.S. Geological Survey geologist examines pumice blocks from the edge or a pyroclastic flow deposit.

(October 17, 1980, Terry A. Leighley, USGS/Sandia Labs)

17. Five more explosive eruptions of Mount St. Helens occurred during 1980, including this spectacular event of July 22. This eruption sent pumice and ash 6 to 11 miles (10-18 km) into the air, and was visible in Seattle, Washington, 100 miles (160 km) to the north. The view here is from the south.

(July 22, 1980, by Michael P. Doukas, USGS)

18. Mount St. Helens has continued to erupt throughout the ensuing years. An explosive eruption on March 19, 1982, sent pumice and ash 9 miles (14 km) into the air, and resulted in a lahar ( the dark deposit on the snow) 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 km) downstream.

(March 21, 1982, by Thomas J. Casadevall, USGS)

19. Plumes of steam, gas, and ash often occur at Mount St. Helens. On clear days they can be seen from Portland, Oregon, 50 miles (81 km) to the south. The plume photographed here rose nearly 3000 feet (1000 m) above the volcano's rim. The view is from Harry's Ridge, five miles (8 km) north of the mountain.

May 19, 1982, by Lyn Topinka, USGS)

20. Since December 1980, eruptions of Mount St. Helens have added material to a dacitic lava dome with the crater, as seen here in this 1984 view from the north. This dome was not the first dome to grow in the crater. In June and August 1980, two domes formed, only to be blasted away by the explosive events of July 22 and October 16.

September 13, 1984, by Lyn Topinka, USGS/CVO)

21. A new dome started growing on October 18,1980. This October dome was 112 feet (34 m) high and 985 feet (300 m) wide, making it taller than a nine-story building and wider than the length of three football fields. This aerial view is from the north.

(October 24, 1980, by Terry A. Leighley, USGS/Sandia Labs)

22. Mount St. Helens dome grows in different ways. From 1980 through 1982 it grew in periodic extrusions of stubby lava flows, called lobes. This pattern changed in February 1983, when growth became continuous and mostly endogenous (internal). Periodic lobe growth, along with endogenous growth, resumed in early 1984. An aerial view of the June 1981 lobe with its "spreading center" is shown here. A spreading center is the area from which new lava slowly emerges during lobe growth. Mount St. Helens' lobes grow at a rate of 3 to 10 feet per hour (1-3 m/hr)

(June 26, 1981, by Daniel Dzurisin, USGS/CVO)

23. This slide shows Mount St. Helens' lava dome in August 1981, as viewed from a photo station 1/2 mile (0.8 km) away. In this view the dome is 535 feet (163 m) high and nearly 1/4 mile (0.4 km) wide, making it taller than a 44-story building (or, nearly the height of the Washington Monument) and wider than the length of four football fields.

(August 22, 1981, by Lyn Topinka, USGS/CVO)

24. This slide shows the lava dome as viewed from the same photo station with the same camera, after five years of growth. The lava dome was 755 feet (230 m) high and 1/2 mile (0.8 km) wide, making it taller than a 66-story building and almost as wide as the length of nine football fields. The dome completely fills the camera's field of view.

August 12, 1985, by Lyn Topinka, USGS/CVO)

25. Two U.S. Geological Survey geologists (one in orange, middle right, near base of dome) are dwarfed by the dome. The geologists stand on snow muddied from recent ashfall. By 1990, the dome had replaced only three percent of the volume removed by the May 18, 1980 eruption. If this rate of growth continues it would take over 200 years to rebuild Mount St. Helens to its pre-1980 size.

(May 26, 1983, by Lyn Topinka, USGS/CVO)

26. The most recent dome-building eruption of Mount St. Helens occurred in October 1986. A new lobe was extruded, increasing the dome's height to 925 feet (282 m), making it taller than a 77-story building. In volume, the dome is nearly 40 times the size of Seattle's Kingdome stadium. In this 30-minute, moon-lit exposure, hot rock from the new lobe is seen glowing on top of the dome. The view is from Harrys Ridge, five miles (8 km) north of the volcano.

(October 22, 1986, at 8:50 p.m., by Lyn Topinka, USGS/CVO)

27. The U.S. Geological Survey has established both periodic and continuous 24-hour monitoring programs of Mount St. Helens to study and predict eruptions. In this slide, geologists use a steel tape to measure the distance across a crack on the crater floor. Widening of cracks is an indication that magma is rising and deforming the area, leading to an eruption. These cracks are generally radial to the dome, like spokes of a wheel.

(May 12, 1981, by Lyn Topinka, USGS/CVO)

28. Geologists use a theodolite and EDM (Electronic Distance Meter) to measure angles and slope-distances to the lava dome. Changes in these angles and distances are used to calculate "deformation rates". An increase in deformation rates is an indication that magma is slowly entering the dome. Deformation rates often reach 30 feet per hour (10 m/hr) as magma rises and the dome expands before extrusion starts. During the winter months, the instrument stations often have to be dug out of the snow before measurements can be made.

(May 26, 1984, by Lyn Topinka, USGS/CVO)

29. Geologists install a seismic station near the dome. The U.S. Geological Survey, in conjunction with the University of Washington, maintains seismic stations at Mount St. Helens. An increase in seismicity (earthquakes) is often the first precursor to an approaching eruption.

(August 4, 1981, by Eugene Y. Iwatsubo, USGS/CVO)

30. Geologists collect gas samples around the dome. Samples are gathered from vents on the dome and crater floor, and are used to monitor changes in chemical composition. Additionally, sulfur dioxide gas is measured from a specially-equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano. During eruptions, emission rates typically increase to 5 to 10 times their pre-eruptive value.

(September 24, 1981, by Thomas J. Casadevall, USGS/CVO)

31. Geologists measure the strength of the magnetic field surrounding the dome. The strength of the field increases as the dome cools and magnetic minerals form. During the eruptions the strength usually changes rapidly as magma heats and deforms the dome.

(June 18, 1984, by Lyn Topinka, USGS/CVO)

32. Geologists do precise leveling to measure changes in the slope of the crater floor, due to moving magma. Changes in slope are also measured electronically by tiltmeters. Tiltmeters allow 24-hour monitoring as the informations is telemetered back to CVO. Other instruments such as displacement meters for measuring cracks, seismometers for measuring earthquakes, gas sensors for measuring gas concentrations, and magnetometers for measuring the magnetic field, are also used for 24-hour monitoring.

( May 1982, by Holly Martinson, USGS)

33. In 1983, the U. S. Geological Survey extended both its periodic and its 24-hour monitoring programs to the top of Mount St. Helens' dome. In this aerial view, three geologists (middle bottom) are busy taking measurements to determine deformation rates.

(April 18, 1988, by Lyn Topinka, USGS/CVO)

34. The U. S. Geological Survey also maintains a network of monitoring stations around the base of Mount St. Helens. Angle and distance measurements to the volcano's flanks are taken periodically to watch for any deformation similar to the 1980 bulge. Pictured here is an instrument station northeast of the volcano.

(May 15, 1989, by Lyn Topinka, USGS/CVO)

35. The May 18, 1980 debris avalanche from Mount St. Helens covered over 24 square miles (62 km of the upper Toutle River valley and blocked tributaries of the North Fork Toutle River. New lakes such as Castle Lake (pictured here) and Coldwater Lake were created.

(March 1984, by Robert L. Schuster, USGS/CVO/Denver)

36. One major concern to people living downstream of Mount St. Helens is a breakout of any of these impounded lakes due to the instability of the debris dams blocking them. Flood waters from a breakout could be more catastrophic than the lahars of May 18, 1980. Gages, such as this Early Warning Gage on Coldwater Lake, have been installed at lakes and streams surrounding the volcano. These gages continuously monitor changes in water levels. Major increases or decreases in levels trigger warnings which are telemetered to the U. S. Geological Survey in Vancouver.

(October 1, 1982, by Lyn Topinka, USGS/CVO)

37. Outlet channels have been built at Castle Lake and Coldwater Lake (shown here) to stabilize water levels and prevent overtopping of the debris dams.

(October 17, 1981, by Lyn Topinka, USGS/CVO)

38. From late 1982 through the spring of 1985, a pump station operated at Spirit Lake to maintain that lake at a safe level. Without pumping, Spirit Lake was estimated to overtop its debris dam within a year. In the spring of 1985 a permanent tunnel was opened, allowing water to drain out of the lake safely. This tunnel is 11 feet (3.4 m) in diameter and more than 1.5 miles (2.5 km) in length. The water level of Spirit Lake is now maintained at approximately 100 feet (30 m) below the estimated overtopping level.

(October 2, 1986, by Lyn Topinka, USGS/CVO)

39. Another major problem to people living downstream of Mount St. Helens is the high sedimentation rates resulting from stream erosion of the volcanic deposits. Streams are continuously downcutting channels, eroding their banks, and eating away at the avalanche and lahar deposits. This material is eventually transported downstream and deposited on the streambeds, decreasing the carrying capacity of the channels and increasing the chances of floods.

(February 22, 1982, by Lyn Topinka, USGS/CVO)

40. 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 (shown here), the Cowlitz, and the Columbia Rivers. By 1987, nearly 140 million cubic yards (110 million m ) 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.

(February 5, 1981, by Lyn Topinka, USGS/CVO)

41. In the spring of 1987, construction of a sediment retention dam on the North Fork Toutle River began. This retention dam is designed to help stop the downstream movement of the sediment near where it begins - on the debris avalanche.

(May 1989, by Steven R. Brantley, USGS/CVO)

42. U. S. Geological Survey hydrologists measure changes in erosion along the stream channels affected by the May 18, 1980 eruption. These measurements are used to study the erosion processes and to estimate the severity of the sedimentation problem. The view here is along the Muddy river drainage, approximately one mile (1.5 km) southeast of the volcano's base. Rod person (lower left) and instrument persons (upper right) give scale.

(June 26, 1981, by Lyn Topinka, USGS/CVO)

43. Hydrologists also measure stream discharge and take water samples to determine how much sediment is suspended in the stream and how much sediment is moving along the streambed.

(April 27, 1985, by Lyn Topinka, USGS/CVO)

44. Fireweed is one species of plantlife which has returned to Mount St. Helens' devastated area. Vegetation began reappearing as early as the summer of 1980 as many small trees and plants were protected by the snowpack on May 18. Seeds, carried by the wind or by animals, also entered the area and grew. By 1985, the ridges surrounding the volcano were covered with new growth.

(August 1984, by Lyn Topinka, USGS/CVO)

45. Animals also are making a comeback. Many smaller animals, such as gophers, mice, frogs, fish, and insects were hibernating below ground or under water on May 18, 1980, and they survived the blast. Larger animals such as bear (whose tracks are shown here), elk, deer, and coyotes have been moving back into the area as their food supplies increase. A mountain goat has even been spotted high on the flanks of the volcano.

(October 1980, by Lyn Topinka, USGS/CVO)

46. BEFORE/AFTER #1: This slide shows Mount St. Helens on May 17, 1980, one day before the devastating eruption. The view is from Johnston's Ridge, six miles (10 km) northwest of the volcano.

(May 17, 1980, by Harry Glicken, USGS/CVO)

47. BEFORE/AFTER #2: This slide shows Mount St. Helens soon after the May 18, 1980 eruption, as viewed from Johnston's Ridge.

(September 10, 1980, by Harry Glicken, USGS/CVO)

48. BEFORE/AFTER #3: This slide shows Mount St. Helens four years after the May 18, 1980 eruption, again as viewed from Johnston's Ridge. Note the growth of the lava dome in the crater and the development of the drainage channels around the volcano's flanks.

(September 24, 1984, by Lyn Topinka, USGS/CVO)

49. BEFORE/AFTER #I: Before the devastating May 18, 1980 eruption, Mount St. Helens was considered to be one of the most beautiful and most frequently-climbed peaks in the Cascade Range. Spirit Lake was a vacation area offering hiking, camping, boating, and fishing.

(photo courtesy of Jim Nieland, U. S. Forest Service/Mount St. Helens National Volcanic Monument)

50. BEFORE/AFTER #2: Mount St. Helens and the devastated area is now within the 110,000-acre Mount St. Helens National Volcanic Monument, under jurisdiction of the United States Forest Service. Visitor centers, interpretive areas, and trails are being established as thousands of tourists, students, and scientists visit the monument daily. Mount St. Helens is once again considered to be one of the most beautiful and interesting of the Cascade volcanic peaks.

(May 19, 1982, by Lyn Topinka, USGS/CVO)