Sand boils, sand volcanoes, or sand blows occur when water under pressure wells up through a bed of sand. [1] The water looks like it is boiling up from the bed of sand, hence the name.
Sand boils, sand volcanoes, or sand blows occur when water under pressure wells up through a bed of sand. [1] The water looks like it is boiling up from the bed of sand, hence the name.
A sand volcano or sand blow is a cone of sand formed by the ejection of sand onto a surface from a central point. The sand builds up as a cone with slopes at the sand's angle of repose. A crater is commonly seen at the summit. The cone looks like a small volcanic cone [2] and can range in size from millimetres to metres in diameter.
The process is often associated with soil liquefaction and the ejection of fluidized sand that can occur in water-saturated sediments during an earthquake. The New Madrid seismic zone exhibited many such features during the 1811–1812 New Madrid earthquakes. [3] Adjacent sand blows aligned in a row along a linear fracture within fine-grained surface sediments are just as common, and can still be seen in the New Madrid area.
These earthquakes also caused the largest known sand boil in the world, which can still be found near Hayti, Missouri and is locally called "The Beach". [4] It is 2.3 kilometers long and covers 55 hectares.
In the past few years, much effort has gone into the mapping of liquefaction features to study ancient earthquakes. [5] The basic idea is to map zones that are susceptible to the process and then go in for a closer look. The presence or absence of soil liquefaction features, such as clastic dikes, is strong evidence of past earthquake activity, or lack thereof.
These are to be contrasted with mud volcanoes , which occur in areas of geyser or subsurface gas venting.
Sand boils can be a mechanism contributing to liquefaction and levee failure during floods. Boil refers to the visible "boiling" movement of coarse sand grains retained in the hole even as finer particles (silts and fine sands) are carried out and deposited on the apron around the boil hole. Sand boils are caused by hydraulic head in levee or dike pushing the water to seep out the other side, most likely during a flood. Sand boils start as simple seeps of laminar flow. With increasing head from rising flood waters, turbulent flow will initiate where the laminar flow leaves the soil to flow freely. Turbulent flow produces soil piping, whereby backward erosion results in a pipe-shaped cavity reaching back into the embankment, initiating at the seep and working through the embankment back to the water source. Once initiated, an unmitigated soil pipe can proceed quickly to embankment failure.
The flow in a sand boil can be slowed, but it is impractical to stop completely. The most effective response to an active sand boil is to stand water over the boil deep enough to reduce the hydraulic gradient and slow the water flow to eliminate turbulence and backward erosion at the head of the pipe. Slower, nonturbulent flow will not be able to move soil particles. The suppressing depth of water is created with sandbags forming a stacked ring around the boil. [6]
During the flood of spring 2011, the United States Army Corps of Engineers had to work to contain the largest active sand boil ever discovered. The sand boil measured nine by 12 meters (30 by 40 feet) and was located in the city of Cairo, Illinois, at the confluence of the Mississippi River and the Ohio River. [7]
An example of this is during the 1989 earthquake in San Francisco when sand boils brought up debris from the 1906 earthquake. This process is a result of liquefaction. By mapping the location of sand boils that erupted in the Marina District during the 1989 Loma Prieta earthquake, scientists discovered the site of a lagoon that existed in 1906. The lagoon developed after the Fair's Seawall was constructed and was later filled in in 1915 in preparation for the Panama–Pacific International Exposition. [8]
A levee, dike, dyke, embankment, floodbank, or stop bank is an elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against flooding of the area adjoining the river. It is usually earthen and often runs parallel to the course of a river in its floodplain or along low-lying coastlines.
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid. In soil mechanics, the term "liquefied" was first used by Allen Hazen in reference to the 1918 failure of the Calaveras Dam in California. He described the mechanism of flow liquefaction of the embankment dam as:
If the pressure of the water in the pores is great enough to carry all the load, it will have the effect of holding the particles apart and of producing a condition that is practically equivalent to that of quicksand... the initial movement of some part of the material might result in accumulating pressure, first on one point, and then on another, successively, as the early points of concentration were liquefied.
A sandbag or dirtbag is a bag or sack made of hessian (burlap), polypropylene or other sturdy materials that is filled with sand or soil and used for such purposes as flood control, military fortification in trenches and bunkers, shielding glass windows in war zones, ballast, counterweight, and in other applications requiring mobile fortification, such as adding improvised additional protection to armored vehicles or tanks.
A geologic hazard or geohazard is an adverse geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions and affect local and regional socio-economics to a large extent.
Kohala is the oldest of five volcanoes that make up the island of Hawaii. Kohala is an estimated one million years old—so old that it experienced, and recorded, the reversal of Earth's magnetic field 780,000 years ago. It is believed to have breached sea level more than 500,000 years ago and to have last erupted 120,000 years ago. Kohala is 606 km2 (234 sq mi) in area and 14,000 km3 (3,400 cu mi) in volume, and thus constitutes just under 6% of the island of Hawaii.
Floodgates, also called stop gates, are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and canals, or they may be designed to stop water flow entirely as part of a levee or storm surge system. Since most of these devices operate by controlling the water surface elevation being stored or routed, they are also known as crest gates. In the case of flood bypass systems, floodgates sometimes are also used to lower the water levels in a main river or canal channels by allowing more water to flow into a flood bypass or detention basin when the main river or canal is approaching a flood stage.
The Herbert Hoover Dike is a dike around the waters of Lake Okeechobee in Florida.
A levee breach or levee failure is a situation where a levee fails or is intentionally breached, causing the previously contained water to flood the land behind the levee.
Paleoliquefaction is any liquefaction features attributed to seismic events occurring before measurements or written records were kept of earthquakes. The study of these features can reveal a great deal about the seismicity of regions where large earthquakes happen infrequently. This is a subset of the broader field of paleoseismology.
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally have bulk densities comparable to those of rock avalanches and other types of landslides, but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water. Debris flows descending steep channels commonly attain speeds that surpass 10 m/s (36 km/h), although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide. The largest prehistoric flows have had volumes exceeding 1 billion cubic meters. As a result of their high sediment concentrations and mobility, debris flows can be very destructive.
Internal erosion is the formation of voids within a soil caused by the removal of material by seepage. It is the second most common cause of failure in levees and one of the leading causes of failures in earth dams, responsible for about half of embankment dam failures.
An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes the dam impervious to surface or seepage erosion. Such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance.
The IJkdijk is a facility in the Netherlands to test dikes and to develop sensor network technologies for early warning systems. Furthermore, the sensor network will be able to detect many water-related environmental factors that affect the health of humans such as pollution and biological changes. Disasters on rivers and coastal waters are also detected.
Earth Revealed: Introductory Geology, originally titled Earth Revealed, is a 26-part video instructional series covering the processes and properties of the physical Earth, with particular attention given to the scientific theories underlying geological principles. The telecourse was produced by Intelecom and the Southern California Consortium, was funded by the Annenberg/CPB Project, and first aired on PBS in 1992 with the title Earth Revealed. All 26 episodes are hosted by Dr. James L. Sadd, professor of environmental science at Occidental College in Los Angeles, California.
The Marina District is a neighborhood located in San Francisco, California. The neighborhood sits on the site of the 1915 Panama–Pacific International Exposition, staged after the 1906 San Francisco earthquake to celebrate the reemergence of the city. Aside from the Palace of Fine Arts, all other buildings were demolished to make the current neighborhood.
In geology, a backswamp is a type of depositional environment commonly found in a floodplain. It is where deposits of fine silts and clays settle after a flood. These deposits create a marsh-like landscape that is often poorly drained and usually lower than the rest of the floodplain.
Relief wells are used both in the natural gas and petroleum industry and in flood control.
Soft-sediment deformation structures develop at deposition or shortly after, during the first stages of the sediment's consolidation. This is because the sediments need to be "liquid-like" or unsolidified for the deformation to occur. These formations have also been put into a category called water-escape structures by Lowe (1975). The most common places for soft-sediment deformations to materialize are in deep water basins with turbidity currents, rivers, deltas, and shallow-marine areas with storm impacted conditions. This is because these environments have high deposition rates, which allows the sediments to pack loosely.
Sedimentation enhancing strategies are environmental management projects aiming to restore and facilitate land-building processes in deltas. Sediment availability and deposition are important because deltas naturally subside and therefore need sediment accumulation to maintain their elevation, particularly considering increasing rates of sea-level rise. Sedimentation enhancing strategies aim to increase sedimentation on the delta plain primarily by restoring the exchange of water and sediments between rivers and low-lying delta plains. Sedimentation enhancing strategies can be applied to encourage land elevation gain to offset sea-level rise. Interest in sedimentation enhancing strategies has recently increased due to their ability to raise land elevation, which is important for the long-term sustainability of deltas.