steeper slope has a larger force parallel to the slope (red arrow) the main features of a rotational landslide

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1995 La Conchita landslide in California 08CO, p.

above it gave way when soaked with too much water Fig. 8-1a, p.

this photograph, which was taken the day after the landslide in

188 talus slope of basalt blocks formed as rocks fell from the

(Columbia River Plateau near Palouse Falls, WA). Fig. 8-2, p.

force parallel to the slope (red arrow) the main features of a

1 1995 La Conchita landslide in California 08CO, p.187 The community of La Conchita, California-- soft marine terrace above it gave way when soaked with too much water Fig. 8-1a, p.188 irrigated avocado field is visible at the top of the terrace in this photograph, which was taken the day after the landslide in 1995 Fig. 8-1b, p.188 talus slope of basalt blocks formed as rocks fell from the cliff and rolled down the slope to rest at their angle of repose (Columbia River Plateau near Palouse Falls, WA). Fig. 8-2, p.189 forces on a mass resting on a slope steeper slope has a larger force parallel to the slope (red arrow) the main features of a rotational landslide Fig. 8-3, p.189 for the gentler slope, the friction force (f) is larger than the force pulling parallel to the slope (F), Fig. 8-4, p.190

Capillary cohesion in the narrow necks between grains pulls the grains together.

191 Water pressure at depth is equal to the load or weight of the overlying water.

191 Water (dark) seeps out of the soil below the sharply defined saturation level

California National Park, Montana Fig. 8-7, p.191 Fig. 8-8, p.

2 Capillary cohesion in the narrow necks between grains pulls the grains together. Fig. 8-5, p.191 Water pressure at depth is equal to the load or weight of the overlying water. Fig. 8-6, p.191 Water (dark) seeps out of the soil below the sharply defined saturation level exposed in a road cut in Glacier 1999 Dana Point landslide north of San Diego, California National Park, Montana Fig. 8-7, p.191 Fig. 8-8, p.192 Filling a reservoir behind a dam raises groundwater in the adjacent slopes, often leading to sliding into the reservoir Fig. 8-9, p.192 Installation of a perforated drainpipe can lower the water table and reduce the chance of sliding. Fig. 8-10, p.193

Low permeability of this shale necessitates many drainpipes Water drains from perforated

Highway 101 north of Garberville, California Fig. 8-11, p.

If the grains collapse to a tighter arrangement, much of the water must be squeezed out.

194 houses on San Francisco Bay fill did not collapse during the 1906 earthquake but

Fig. 8-13, p.194 Fig. 8-14, p.195 http://en.wikipedia.

edu/courses/cee522/rissalandslide/rissa.

3 Low permeability of this shale necessitates many drainpipes Water drains from perforated groundwater-drainage pipes in shale road cut on U.S. Highway 101 north of Garberville, California Fig. 8-11, p.193 Loosely packed grains provide large pore spaces for water. If the grains collapse to a tighter arrangement, much of the water must be squeezed out. Fig. 8-12, p.194 houses on San Francisco Bay fill did not collapse during the 1906 earthquake but settled as the fill liquefied Three typical types of ground failure during liquefaction Fig. 8-13, p.194 Fig. 8-14, p tml Clay grains deposited in random orientation have especially large pore spaces a house of cards arrangement. After collapse, compacted clays take up much less space so water in pore spaces must escape. Fig. 8-15, p.195 Lemieux flow in a horizontal terrace of the Leda Clay of the St. Lawrence River Valley near Ottawa, Ontario, settled and flowed into the adjacent river on 6/20/93 Fig. 8-16, p.195

html Rissa Landslide, 1978 near Rissa Norway

a dangerous rockfall area above the Trans

9 earthquake on the Denali Fault 2003 caused

Highway 1 at mouth of Topanga Canyon, CA, west

4 ashington.edu/courses/ cee522/rissalandslide/ rissa.html Rissa Landslide, 1978 near Rissa Norway The Northridge earthquake caused a swarm of landslides Fig. 8-17a, p.196 Mitigation: installing heavy wire mesh over a dangerous rockfall area above the Trans Canada Highway. Magn. 7.9 earthquake on the Denali Fault 2003 caused landslide onto Black Rapids Glacier, Alaska Range Fig. 8-17b, p.196 Fig. 8-18, p.196 Workers drill and bolt a rock cliff above Highway 1 at mouth of Topanga Canyon, CA, west of Los Angeles Fig. 8-19a, p.197 Rockbolts and shotcrete stabilize a heavily fractured road cut below houses in Acapulco, Mexico Fig. 8-19b, p.197

Subsidence and seaward spreading of the marine

beds slope toward and daylight over a coastal

trough formed at the head of the L Street

199 Marble Canyon, Arizona, recent rockfall

5 Subsidence and seaward spreading of the marine terrace in Anchorage Steeply dipping limestone beds slope toward and daylight over a coastal highway near Sorento, Italy This dropped trough formed at the head of the L Street landslide Fig. 8-20, p.197 Fig. 8-21, p.197 Subtle evidence! hummocky landslide terrain is near Gardena, north of Boise, Idaho Fig. 8-22, p.198 Table 8-1, p.199 Marble Canyon, Arizona, recent rockfall debris forms talus fallen from the visible scar on the cliff above. Fig. 8-23, p.199 North Cascades HWY November 10, 2003 Fig. 8-24, p.199

Some rockfall problems arise where a strong layer such as sandstone overlies a weak layer

200 runout distance traveled by a debris avalanche depends principally on the height of

The values are variable, but an approximation is provided by the formula above: Sidebar

5-meter boulder crushed the living room, bathroom, and part of the bedroom of this house

The source of the boulders was a massive sandstone and conglomerate cliff above the

The man at left provides scale. Fig. 8-26, p.201 Fig. 8-27, p.

6 Some rockfall problems arise where a strong layer such as sandstone overlies a weak layer such as shale or clay in Pennsylvania. Fig. 8-25, p.200 runout distance traveled by a debris avalanche depends principally on the height of the mass before it falls and therefore its potential energy. The values are variable, but an approximation is provided by the formula above: Sidebar 8-4, p.200 A 4.5-meter boulder crushed the living room, bathroom, and part of the bedroom of this house at Rockville, Utah, near Zion National Park at 5:38 A.M. on October 18, The source of the boulders was a massive sandstone and conglomerate cliff above the location shown in Figure The boulder is partly visible middle right. The man at left provides scale. Fig. 8-26, p.201 Fig. 8-27, p.201 layers and parallel orientation of micas in the schist almost parallel to the slope at Madison slide headscarp. a)the Madison slide collapsed into the Madison River canyon and continued upslope to the north, left to right. It dammed the river to form Earthquake Lake Fig. 8-28a, p.202 Fig. 8-28b, p.202

Frank slide peeled off the whole east face of Turtle

before and after the Frank slide across the valley and

buried the town of Yungay cross section shows the Elm,

slate quarry that set it off. Fig. 8-31, p.204 Fig.

205 Mclure slide south of Aspen, Colorado, is

7 Frank slide peeled off the whole east face of Turtle Mountain and spread a bouldery limestone deposit slope before and after the Frank slide across the valley and up the slope to the west. Fig. 8-29, p.203 Fig. 8-30, p.203 Mount Nevados Huascarán debris avalanche in 1970 buried the town of Yungay cross section shows the Elm, Switzerland, debris avalanche and the location of the slate quarry that set it off. Fig. 8-31, p.204 Fig. 8-32, p.205 Mclure slide south of Aspen, Colorado, is notorious for continuing to slide. The car plunged off the severed Rotation of a slump block Blackfoot landslide in Montana road in 1994 Fig. 8-33, p.206 Fig. 8-34, p.206

A house begins to break up in a series of rotational

Highway 101 near Garberville, in northern California

landslide at Newport, Oregon (see arrow). Fig. 8-37, p.

208 sackung features in the high mountains of British

8 A house begins to break up in a series of rotational slumps in Colorado River bluffs, Grand Junction, Colorado Fig. 8-35, p.207 Fig. 8-36, p.207 Heavy boulders are often piled on the lower part of a slide to resist movement. This road, cut through a landslide on U.S. Highway 101 near Garberville, in northern California Crushed rock is scattered along the failure surface of a landslide at Newport, Oregon (see arrow). Fig. 8-37, p.208 Fig. 8-38, p.208 sackung features in the high mountains of British Columbia A section of coastal cliff at the edge of Puget Sound, near Seattle, collapsed, crushing and burying a home on the narrow strip of beach Fig. 8-39, p.208 Fig. 8-40, p.209

$400 million = most expensive single landslide event in U.S.

groundwater levels from heavy spring rains Within a few weeks, the slide dammed the Spanish Fork

Water behind the slide dam submerged the town of Thistle. Fig. 8-41, p.

209 rainfall Slumgullion earthflow of southwestern Colorado --volcanic rock peaks in the

Washington at Kelso; > 60 homes destroyed spreading out into Cristobal Lake in the lower right

9 $400 million = most expensive single landslide event in U.S. history The 1983 Thistle landslide se of Salt Lake City, Utah, began in response to rising groundwater levels from heavy spring rains Within a few weeks, the slide dammed the Spanish Fork River and took out U.S. Highway 6 and a major railroad line. Water behind the slide dam submerged the town of Thistle. Fig. 8-41, p.209 October 1985, a landslide destroyed 120 houses in Mamayes, Puerto Rico, and killed at least 129 people. The catastrophic block slide was triggered by a tropical storm with extremely heavy Fig. 8-42, p.209 rainfall Slumgullion earthflow of southwestern Colorado --volcanic rock peaks in the background are heavily altered to slippery clays, Aldercrest landslide in southwestern Washington at Kelso; > 60 homes destroyed spreading out into Cristobal Lake in the lower right Fig. 8-43, p.209 Fig. 8-44, p.209 disastrous 1963 Vaiont slide in northeastern Italy moved catastrophically on weak layers of shale north south cross section shows the Vaiont Reservoir area, preslide mass, and landslide within limestone beds parallel to the mountain face Fig. 8-45, p.210 Fig. 8-46, p.211

stronger layer over weak clays may fail by

Parts of the spreading mass may drop as it

of the Wasatch 1996 debris-flow channel, a

Dodson Front behind Salt Lake City, Utah,

10 stronger layer over weak clays may fail by lateral spreading. Parts of the spreading mass may drop as it spreads. Fig. 8-47, p.212 Palm Springs Fig. 8-48, p.212 debris flows from the huge fault scarp of the Wasatch 1996 debris-flow channel, a tributary to the Columbia River, near Dodson Front behind Salt Lake City, Utah, in 1983 Fig. 8-49, p.212 Fig. 8-50, p.213 debris flow in the Andes of northwestern Argentina Slide Mountain, Nevada, southwest of Reno in May of 1983 Fig. 8-51, p.213 Fig. 8-52, p.213

This diagram shows the distribution of grain sizes and water in a

214 May 1998, a muddy debris flow from the steep hillside to the

mudflows that poured down a valley from Mount Rainier 500 years ago.

do so again House buried by debris flow Fig. 8-55, p.215 Fig. 8-56, p.

collapsed when debris-fl ow boulders crushed key support columns.

11 This diagram shows the distribution of grain sizes and water in a debris flow. Fig. 8-53, p.214 May 1998, a muddy debris flow from the steep hillside to the right of this house in Siano, Italy, east of Mount Vesuvius Fig. 8-54, p.215 The small community of Orting, Washington, is built on huge mudflows that poured down a valley from Mount Rainier 500 years ago. Earlier mudflows filled the same valley; undoubtedly, mudflows will do so again House buried by debris flow Fig. 8-55, p.215 Fig. 8-56, p.215 The end of this apartment building on the Caraballeda fan collapsed when debris-fl ow boulders crushed key support columns. The largest boulder is more than 2 meters high. May 1998, a muddy debris flow from the steep hillside to the right of this house in Siano, Italy, east of Mount Vesuvius Fig. 8-57a, p.216 Fig. 8-57b, p.216

Venezuela were crushed as the slopes gave way

was built in Rubio Canyon, north of Pasadena,

debris- flow dam Debris basin north of Pasadena

California. Fig. 8-60, p.218 Fig. 8-61, p.

Creek, south of Hamilton, Montana, in July

12 Venezuela were crushed as the slopes gave way in the A modern debris-flow collection basin was built in Rubio Canyon, north of Pasadena, California. saturating rain Fig. 8-58, p.217 Fig. 8-59, p storm filled the basin behind this debris- flow dam Debris basin north of Pasadena and overtopped the dam at La Crescenta, California. Fig. 8-60, p.218 Fig. 8-61, p.218 Note abrasion line on trees Sleeping Child Creek, south of Hamilton, Montana, in July 2001; Note scarring and abrasion of bark. Tumalt Creek, east of Portland, Oregon Fig. 8-62, p.219 Fig. 8-63, p.219

fast-moving mudflows racing right to left

220 Soil creep produces a slow downslope

13 fast-moving mudflows racing right to left down the valley A large earthquake on January 13, 2001, triggered this devastating mudslide in a middle-class subdivision in Colonia Las Colinas, El Salvador. It killed ~585. from Mount Pinatubo in the Philippines Fig. 8-64, p.220 Fig. 8-65, p.220 Soil creep produces a slow downslope movement of the upper layers of soil or soft rocks. Pistol-butt trees are often a signal of soil creep Fig. 8-66, p.221 Fig. 8-67, p.221 Fig. 8-68, p.221 Table 8-2, p.222

14 distribution of landslide-prone areas in the United States. Table 8-3, p.223 Fig. 8-69, p.225 hummocks deposited as a massive landslide from Mount Shasta, visible in the upper left. This slide occurred between 300,000 and 380,000 yr ago and was 25 km 3 Fig. 8-70, p.225

Mass Wasting. Revisit: Erosion, Transportation, and Deposition

Mass Wasting. Revisit: Erosion, Transportation, and Deposition Mass Wasting Revisit: Erosion, Transportation, and Deposition While landslides are a normal part of erosion and surface processes, they can be very destructive to life and property! - Mass wasting: downslope