Geology topics
Jon J. Major
Publications and source records attributed to Jon J. Major.
Assessment of landslide hazards resulting from the February 13, 2001, El Salvador earthquake; a report to the government of El Salvador and the U. S. Agency for International Development
On February 13, 2001, a magnitude 6.5 earthquake occurred about 40 km eastsoutheast of the capital city of San Salvador in central El Salvador and triggered thousands of landslides in the area east of Lago de Ilopango. The landslides are concentrated in a 2,500-km2 area and are particularly abundant in areas underlain by thick deposits of poorly consolidated, late Pleistocene and Holocene Tierra Blanca rhyolitic tephras that were erupted from Ilopango caldera. Drainages in the tephra deposits are deeply incised, and steep valley walls failed during the strong shaking. Many drainages are clogged with landslide debris that locally buries the adjacent valley floor. The fine grain-size of the tephra facilitates its easy mobilization by rainfall runoff. The potential for remobilizing the landslide debris as debris flows and in floods is significant as this sediment is transported through the drainage systems during the upcoming rainy season. In addition to thousands of shallow failures, two very large landslides occurred that blocked the Rio El Desague and the Rio Jiboa. The Rio El Desague landslide has an estimated volume of 1.5 million m3, and the Rio Jiboa landslide has an estimated volume of 12 million m3. Field studies indicate that catastrophic draining of the Rio El Desague landslide-dammed lake would pose a minimal flooding hazard, whereas catastrophic draining of the Rio Jiboa lake would pose a serious hazard and warrants immediate action. Construction of a spillway across part of the dam could moderate the impact of catastrophic lake draining and the associated flood. Two major slope failures on the northern side of Volcan San Vicente occurred in the upper reaches of Quebrada Del Muerto and the Quebrada El Blanco. The landslide debris in the Quebrada Del Muerto consists dominantly of blocks of well-lithified andesite, whereas the debris in the Quebrada El Blanco consists of poorly consolidated pyroclastic sediment. The large blocks of lithified rock in Quebrada Del Muerto are unlikely to be remobilized during the rainy season; whereas, the sandy and silty landslide debris in the channel of Quebrada El Blanco is susceptible to remobilization as debris flows that could extend into populated areas on the lower slopes of the volcano. Around the northern and eastern shore of Lago de Ilopango, earthquake-induced liquefaction and lateral-spreading landslides caused local damage to homes and other structures; this damage was most prevalent in the village of San Agustin. San Agustin is also potentially threatened by floods because it is located on the alluvial fan of the Quebrada El Chaguite drainage basin, which contains hundreds of landslides that have choked numerous small channels with volcanic tephra. As the easily eroded tephra is transported down the drainage system and deposited on the alluvial fan, it could clog the currently active channel with sediment, divert the stream into a new channel, and possibly direct flow through San Agustin, causing more damage and destruction
Evolution and timing of suspended-sediment transport following the 1980 Mount St. Helens eruption
No abstract available.
Gravity-driven consolidation of granular slurries: Implications for debris-flow deposition and deposit characteristics
No abstract available.
Mount Hood - history and hazards of Oregon's most recently active volcano
Explore the source record for details and available documents.
Experimental testing of flexible barriers for containment of debris flows
In June 1996, six experiments conducted at the U.S. Geological Survey Debris Flow Flume demonstrated that flexible, vertical barriers constructed of wire rope netting can stop small debris flows. All experimental debris flows consisted of water-saturated gravelly sand with less than two percent finer sediment by weight. All debris flows had volumes of about 10 cubic meters, masses of about 20 metre tons, and impact velocities of 5 to 9 meters per second. In four experiments, the debris flow impacted pristine, unreformed barriers of varying design; in the other two experiments, the debris flow impacted barriers already loaded with sediment from a previous flow. Differences in barrier design led to differences in barrier performance. Experiments were conducted with barriers constructed of square-mesh wire-rope netting with 30centimeter, 20centimeter, and 15 centimeter mesh openings as well as 30centimeter diameter interlocking steel rings. In all cases, sediment cascading downslope at the leading edge of the debris flows tended to spray through the nets. Nets fitted with finer-mesh chain link or chicken wire liners contained more sediment than did unlined nets, and a ring net fitted with a synthetic silt screen liner contained nearly 100 percent of the sediment. Irreversible net displacements of up to 2 meters and friction brake engagement on the support and anchor cables dissipated some of the impact energy. However, substantial forces developed in the steel support columns and the lateral and tie-back anchor cables attached to these columns. As predicted by elementary mechanics, the anchor cables experienced larger tensile forces when the support columns were hinged at the base rather than bolted rigidly to the foundation. Measured loads in the lateral anchor cables exceeded those in the tie-back anchor cables and the load cell capacity of 45 kilo-Newtons. Measurements also indicated that the peak loads in the tie- back anchors were highly transient and occurred at the points of maximum momentum impulse to the net.
Pebble orientation on large, experimental debris-flow deposits
Replicable, pronounced orientation of discoid pebbles (≥8 mm) embedded on surfaces of large (∼10 m 3 ) experimental debris-flow deposits reveals that strongly aligned, imbricate fabric can develop rapidly over short distances in mass flows. Pebble long axes aligned subparallel to deposit margins as well as subparallel to margins of surge waves arrested within the deposits. Pebble alignment exhibited modes both parallel to ( a(p) ), the primary flow direction; intermediate axes dipped preferentially inward from surge-wave margins ( b(i) orientation). Repetitive development of margin-parallel, imbricate fabric distributed across deposit surfaces provides compelling evidence that deposits formed dominantly through progressive incremental accretion rather than through simple en masse emplacement. Pronounced fabric along deposit and arrested surge-wave margins reflects significant grain interaction along flow margins. This sedimentological evidence for significant marginal grain interaction complements theoretical analyses (Iverson, 1997) and other experimental data (Major, 1996; Iverson, 1997) that indicate that resistance along flow margins is an important factor affecting debris-flow deposition. The fabric on the experimental deposits demonstrates that debris flows can develop strongly imbricate particle orientation that mimics fabric developed during fluvial deposition. Particle shape and local stress fields appear to have more control over fabric development than does general depositional process. Other criteria in addition to particle orientation are needed to discriminate mass flow from fluvial gravel deposits and to unravel depositional history.
Comment on Verification of vertically rotating flume using non-Newtonian fluids
No abstract available.
Book review of Clean Water: The citizen’s complete guide to water quality and water pollution control
No abstract available.
Response of flexible wire rope barriers to debris-flow loading
No abstract available.
Experimental analysis of debris-flow deposition--process and effects of pore-fluid pressure
No abstract available.
Watershed disturbance and lahars on the east side of Mount Pinatubo during the mid-June 1991 eruptions
No abstract available.
Experimental studies of deposition at a debris-flow flume
Geologists commonly infer the flow conditions and the physical properties of debris flows from the sedimentologic, stratigraphic, and morphologic characteristics of their deposits. However, such inferences commonly lack corroboration by direct observation because the capricious nature of debris flows makes systematic observation and measurement of natural events both difficult and dangerous. Furthermore, in contrast to the numerous experimental studies of water flow and related fluvial deposition, few real-time observations and measurements of sediment deposition by large-scale mass flow of debris under controlled conditions have been made. Recent experiments at the U.S. Geological Survey debris-flow flume in the H. J. Andrews Experimental Forest, Oregon (Iverson and others, 1992) are shedding new insight on sediment deposition by debris flows and on the veracity of methods commonly used to reconstruct flow character from deposit characteristics.
The eruption of Redoubt Volcano, Alaska, December 14, 1989-August 31, 1990
No abstract available.
Snow and ice perturbation during historical volcanic eruptions and the formation of lahars and floods
Historical eruptions have produced lahars and floods by perturbing snow and ice at more than 40 volcanoes worldwide. Most of these volcanoes are located at latitudes higher than 35°; those at lower latitudes reach altitudes generally above 4000 m. Volcanic events can perturb mantles of snow and ice in at least five ways: (1) scouring and melting by flowing pyroclastic debris or blasts of hot gases and pyroclastic debris, (2) surficial melting by lava flows, (3) basal melting of glacial ice or snow by subglacial eruptions or geothermal activity, (4) ejection of water by eruptions through a crater lake, and (5) deposition of tephra fall. Historical records of volcanic eruptions at snow-clad volcanoes show the following: (1) Flowing pyroclastic debris (pyroclastic flows and surges) and blasts of hot gases and pyroclastic debris are the most common volcanic events that generate lahars and floods; (2) Surficial lava flows generally cannot melt snow and ice rapidly enough to form large lahars or floods; (3) Heating the base of a glacier or snowpack by subglacial eruptions or by geothermal activity can induce basal melting that may result in ponding of water and lead to sudden outpourings of water or sediment-rich debris flows; (4) Tephra falls usually alter ablation rates of snow and ice but generally produce little meltwater that results in the formation of lahars and floods; (5) Lahars and floods generated by flowing pyroclastic debris, blasts of hot gases and pyroclastic debris, or basal melting of snow and ice commonly have volumes that exceed 10 5 m 3 . The glowing lava (pyroclastic flow) which flowed with force over ravines and ridges...gathered in the basin quickly and then forced downwards. As a result, tremendously wide and deep pathways in the ice and snow were made and produced great streams of water (Wolf 1878).