Geology Exam 4 (Ch. 16,18, 21,& 23)
Pumped Water-Storage
(in hydroelectric systems) a method of using power at a period of low demand to pump water back up to a high storage reservoir so that it can be released to generate electricity at a period of peak demand.
Cross-Sectional Shape
-A slice taken across the channel -Determines, to a large extent, the amount of flow in contact with the banks and bed of the channel
Basic Laws governing radiation:
-All objects, at whatever temperature, emit radiant energy -Hotter objects radiate more total energy per unit area than do colder objects -The hotter the radiating body, the shorter the wavelength of maximum radiation -Objects that are good absorbers of radiation are good emitters as well
Hydraulic Fracturing
-Fracking -Shatters the shale, opening up cracks through which the natural gas can flow into wells and then be brought to the surface
Ice-Jam Floods
-Frozen rivers are especially susceptible -As the level of a stream rises, it breaks up ice and creates ice floes that can accumulate on channel obstructions
Continental Ice Sheets
-Greenland -Antarctica
Sediment Production
-Most of the sediment is derived -Located in the headwaters region of the river system
Regional Floods
-Seasonal -Rapid melting of snow in spring and/or heavy spring rains often overwhelm rivers
Uranium-235
-The only naturally occurring isotope that is readily fissionable, and it's therefore the primary fuel used in nuclear power plants
Sinuosity
-The sinuosity of a stream is a measure of how much it is meandering -Sinuosity= channel distance/linear (or valley) distance
Slope
-The slope of the channel (s) between 2 points is the ratio of the vertical change (Y) in stream elevation divided by the horizontal distance (x) between the 2 points -S= Y/X
Discharge
-The volume of water flowing past a certain point in a given unit of time -The rate of flow= volume/unit time
100-Year Flood
-This described the recurrence interval which is an estimate of how often a flood of a given size can be expected to occur. -The phrase doesn't mean that 100 years must pass between each flood or equal or greater magnitude -It means there is a 1% probability in a given year for a flood of that size
Milankovitch formulated a comprehensive mathematical model based on the following elements:
-Variation in the shape (eccentricity) of Earth's orbit about the Sun -Changes in obliquity-that is, changes in the angle that the axis makes with the plane of Earth's orbit -The wobbling of Earth's axis, called precession
Sediment Deposition
-When a river reaches the ocean or another large body of water, it slows and the energy to transport sediment is greatly reduced -Most of the sediments either accumulate at the mouth of the river to form a delta, are reconfigured by wave action to form a variety of coastal features, or are moved far offshore by ocean currents
Trunk Streams
-When in balance, the amount of sediment eroded from their banks equals the amount deposited elsewhere in the channel -Not a source of sediment, nor do they accumulate or store it
The following geologic factors favor a geothermal reservoir of commercial value:
1) A potent source of heat 2) Large and porous reservoirs which channels connected to the heat source 3) A cap of low-permeability rocks
World's 10 Largest Rivers
1) Amazon 2) Congo 3) Yangtze 4) Brahmaputra 5) Ganges 6) Yenisei 7) Orinoco 8) Mississippi 9) Lena 10) Parana
Several Factors influence flow velocities and, therefore, control a stream's potential to do "work". These factors include:
1) Channel slope or gradient 2)Channel cross-sectional shape 3) Channel size and roughness 4) Discharge, or the amount of water flowing in the channel
Geologists divide glacial drift into 2 distinct types:
1) Materials deposited directly by the glacier, which are known as till 2) Sediments laid down by glacial meltwater, called stratified drift
Largest U.S. Rivers
1) Mississippi 2) St. Lawerence 3) Ohio 4) Columbia 5) Yukon 6) Missouri 7) Tennessee
This differential erosion by ice is largely controlled by 4 factors:
1) Rate of glacial movement 2) Thickness of the ice 3) Shape, abundance, & hardness of the rock fragments contained in the ice at the base of the glacier 4) The erodibility of the surface beneath the glacier
Cirque
A amphitheater-shaped basin at the head of a glaciated valley produced by frost wedging and plucking
Pater Noster Lakes
A chain of small lakes in a glacial trough that occupies basins created by glacial erosion
Point Bars
A crescent-shaped accumulation of sand and gravel deposited on the inside of a meander
Longitudinal Profile
A cross section of a stream channel along its descending course from the head to the mouth
Sunspot
A dark area on the Sun that is associated with powerful magnetic storms that extend from the Sun's surface deep into the interior
Crevasse
A deep crack in the brittle surface of a glacier
Placers
A deposit formed when heavy minerals are mechanically concentrated by currents, most commonly streams and waves. Placers are sources of gold, tin, platinum, diamonds, and other valuable minerals
Rectangular Drainage Pattern
A drainage pattern characterized by numerous right angle bends that develops on jointed or fractured bedrock
Alluvial Fans
A fan-shapped deposit of sediment formed when a stream's slope is abruptly reduced
Oil Shale
A fine-grained sedimentary rock that contains a solid mixture of organic compounds from which liquid hydrocarbons called shale oil can be produced
Terrace
A flat, benchlike structure produced by a stream, which was left elevated as the stream cut downward
Ablation
A general term for the loss of ice and snow from a glacier
Oil Trap
A geologic structure that allows for significant amounts of oil and gas to accumulate
Alpine Glaciers
A glacier confined to a mountain valley, which in most instance had previously deposited in the valley
Piedmont Glaciers
A glacier that forms when one or more alpine glaciers emerge from the confining walls of mountain valleys and spread out to create a broad sheet in the lowlands at the base of the mountains
Proglacial Lakes
A lake created when a glacier acts a dam blocking the flow of a river or trapping glacial meltwater. The term refers to the position of such lakes just beyond the outer limits of a glacier
Pluvial Lakes
A lake formed during a period of increased rainfall. For example, this occurred in many nonglaciated areas during periods of ice advance elsewhere
Incised Meanders
A meandering channel that flows in a steep, narrow valley. It forms either when an area is uplifted or when the base level drops
Competence
A measure of a stream's ability to transport particles based on size rather than quantity
Basal Slip
A mechanism of glacial movement in which the ice mass slides over the surface below
Oxygen Isotope Analysis
A method of deciphering past temperatures based on the precise measurement of the ratio between two isotopes of oxygen, 16^O and 18^O. Analysis is commonly made of seafloor sediments and cores from ice sheets
Nonmetallic Mineral Resources
A mineral resource that is not a fuel or processed for the metals it contains
Vein Deposits
A mineral that fills a fracture or fault in a host rock. Such deposits have a sheetlike, or tabular, form
Glacial Trough
A mountain valley that has been widened, deepened, and straightened by a glacier
Arete
A narrow, knifelike ridge separating two adjacent glaciated valleys
Kame Terrace
A narrow, terracelike mass of stratified drift deposited between a glacier and an adjacent valley wall
Cap Rock
A necessary part of an oil trap. The cap rock is impermeable and hence keeps upwardly mobile oil and gas from escaping at the surface
Col
A pass between mountain valleys where the headwalls of two cirques intersect
Water Gap
A pass through a ridge or mountain in which a stream flows
Surge
A period of rapid glacial advance. Surges are typically sporadic and short-lived
Plucking
A process by which pieces of bedrock are lifted out of place by a glacier
Corrosion
A process in which rock is gradually dissolved by the flowing water
Horn
A pyramid-like peak formed by glacial action in 3 or more cirques surrounding a mountain summit
Outwash Plain
A relatively flat, gently sloping plain consisting on materials deposited by melt-water streams in front of the margin of an ice sheet
Valley Train
A relatively narrow body of stratified drift deposited on a valley floor by meltwater streams that issue from the terminus of an alpine glacier
Lateral Moraine
A ridge of till along the sides of a valley glacier composed primarily of debris that fell to the glacier from the valley walls
Medial Moraine
A ridge of till formed when lateral moraines from 2 coalescing alpine glaciers join
End Moraine
A ridge of till marking a former position of the front of a glacier
Tillite
A rock formed when glacial till is lithified
Distributary
A section of a stream that leaves the main flow
Esker
A sinuous ridge composed largely of sand and gravel deposited by a stream flowing in a tunnel beneath a glacier near its terminus
Tarn
A small lake in a cirque
Kame
A steep-sided hill composed of sand and gravel, originating when sediment collected in openings in stagnant glacial ice
Fjords
A steep-sided inlet of the sea formed when a glacial trough was partially submerged
Alluvial Channels
A stream channel in which the bed and banks are composed largely of unconsolidated sediment (alluvium) that was previously deposited in the valley
Dendritic Drainage Pattern
A stream system that resembles the pattern of a branching tree
Antecedent Stream
A stream that continued to downcut and maintain its original course as an area along its course was uplifted by faulting or folding
Superposed Stream
A stream that cuts through a ridge lying across its path. The stream established its course on uniform layers at a higher level without regard to underlying structures and subsequently downcut
Graded Stream
A stream that has the correct channel characteristics to maintain exactly the velocity required to transport the material supplied to it
Drumlins
A streamlined symmetrical hill composed of glacial till. The steep side of the hill faces the direction from which the ice advanced
Trellis Drainage Pattern
A system of streams in which nearly parallel tributaries occupy valleys cut in folded strata
Radial Drainage Pattern
A system of streams running in all directions, away from a central elevated structure, such as a volcano
Outlet Glaciers
A tongue of ice normally flowing rapidly outward from an ice cap or ice sheet, usually through mountainous terrain to the sea
Yazoo tributary
A tributary that flows parallel to the main stream because a natural levee is present
Hanging Valleys
A tributary valley that enters a glacial trough at a considerable height above the floor of the trough
Plastic Flow
A type of glacial movement that occurs within a glacier, below a depth of approximately 50 meters (165 ft), in which the ice is not fractured
Pegmatites
A very coarse-grained igneous rock (typically granite) commonly found as a dike associated with a large mass of plutonic rock that has smaller crystals. Crystallization in a water-rich environment is believed to be responsible for the very large crystals
Ice sheets
A very large, thick mass of glacial ice flowing outwards in all directions from one or more accumulation centers
About 18,000 years ago glacial ice not only covered Greenland and Antarctica but also large portions of North America, Europe, and Siberia. This date in Earth history is appropriately known as the Last Glacial Maximum. The term implies that there were other glacial maximums.
About 18,000 years ago glacial ice not only covered Greenland and Antarctica but also large portions of North America, Europe, and Siberia. This date in Earth history is appropriately known as the Last Glacial Maximum. The term implies that there were other glacial maximums.
Mineral Resources
All discovered and undiscovered deposits of a useful mineral that can be extracted now or at some time in the future
Reserves
Already identified deposits from which minerals can be extracted profitably
Ice-Contact Deposit
An accumulation of stratified drift deposited in contact with a supporting mass of ice
Glacial Drift
An all-embracing term for sediments of glacial origin, no matter how, where, or in what shape they were deposited
Roche Moutonee
An asymmetrical knob of bedrock that is formed when glacial abrasion smoothes the gentle slope facing the advancing ice sheet and plucking steepens the opposite side as the ice overrides the knob
Natural Levee
An elevated landform composed of alluvium that parallels some streams and acts to confine their waters, except during floodstage
Recessional Moraines
An end moraine formed as the ice front stagnated during glacial retreat
Glacial Erratics
An ice-transported boulder that was not derived from the bedrock near its present site
Divide
An imaginary line that separates the drainage of two streams, often found along a ridge
Ground Moraine
An undulating layer of till deposited as an ice front retreats
Disseminated Deposit
Any economic mineral deposit in which the desired mineral occurs as scattered particles in the rock but in sufficient quantity to make the deposit an ore
As ice melts, material transported by the glacier is released and falls to the ocean floor. The rocks are called dropstones.
As ice melts, material transported by the glacier is released and falls to the ocean floor. The rocks are called dropstones.
Positive-Feedback Mechanism
As used in climatic change, any effect that acts to reinforce the initial change
Negative-Feedback Mechanism
As used in climatic change, any effect that is opposite the initial change and tends to offset it
Knickpoint
Because of the increased gradient (slope), the stream concentrates its erosive energy on the resistant rock along an area called a knickpoint
Bankfull
Before water starts to inundate the floodplain
Flood-Control Dams
Built to store floodwater and then release it slowly, in a controlled manner
Chapter 16
Chapter 16
Chapter 18
Chapter 18
Chapter 21
Chapter 21
Chapter 23
Chapter 23
Potholes
Circular depressions
Gas Hydrates
Compact chemical structures made of water and natural gas (usually methane) that occur in permafrost and under the ocean floor at depths greater than 525 meters
Foreset Beds
Composed of coarse particles that drop almost immediately upon entering the water to form layers that slope downcurrent from the delta front
Stream Valley
Consists of a channel and the surrounding terrain that directs water to the stream
Bedrock Channels
Cut into the underlying strata and typically form in the headwaters of river systems where streams have steep slopes
Proxy Data
Data gathered from natural recorders of climate variability such as tree rings, ice cores, and ocean-floor sediments
Topset Beds
Deposited during flood stage
Stream Piracy
Diversion of the drainage of one stream that results from the headward erosion of another stream
Continental Divide
Drainage divides range in scale from a small ridge separating two gullies on a hillside to a continental divide that splits an entire continent into enormous drainage basins
Artificial Levees
Earthen mounds built on river banks to increase the volume of water the channel can hold
Hydroelectric Power
Electricity generated by falling water that is used to drive turbines
Turbulent Flow
Erratic movement of water often characterized by swirling, whirlpool-like eddies. Most streamflow is of this type.
Climate System
Exchanges of energy and moisture occurring
Suspended Load
Fine sediment carried within the body of flowing water or air
Bottomset Beds
Finer silts and clays settle away from the mouth in nearly horizontal layers
Runoff
Flows over the surface
Frictional drag with the bedrock floor causes the lower portions of the glacier to move more slowly.
Frictional drag with the bedrock floor causes the lower portions of the glacier to move more slowly.
Fossil Fuel
General term for any hydrocarbon that may be used as a fuel, including coal, oil, natural gas, bitument from tar sands, and shale oil
Firn
Granular, recrystallized snow. A transitional stage between snow and glacial ice.
Rock Flour
Ground-up rock produced by the grinding effect of a glacier
Braided Channels
Interwoven channels
Channelization
Involves altering a stream channel in order to make the flow more efficient
Saltation
Jumping or skipping along the streambed
Lake Bonneville was nearly the same size as present-day Lake Michigan. As the ice sheets waned, the climate again grew more arid, and the lake levels lowered in response. Although most of the lakes completely disappeared, a few small remnants of Lake Bonneville remain, the Great Salt Lake being the largest and best known.
Lake Bonneville was nearly the same size as present-day Lake Michigan. As the ice sheets waned, the climate again grew more arid, and the lake levels lowered in response. Although most of the lakes completely disappeared, a few small remnants of Lake Bonneville remain, the Great Salt Lake being the largest and best known.
Back Swamps
Marshes
Oil Sands
Mixtures of clay, sand, and water, and a black viscous form of petroleum known as bitumen
Much of the material acquired and transported by a glacier is ultimately deposited by streams of glacial meltwater flowing on, within, beneath, and beyond a glacier. This sediment is termed stratified drift.
Much of the material acquired and transported by a glacier is ultimately deposited by streams of glacial meltwater flowing on, within, beneath, and beyond a glacier. This sediment is termed stratified drift.
Geothermal Energy
Natural steam used for power generation
Sheet Flow
Runoff initially flows in broad, thin sheets across slopes
Runoff= Rainfall - Infiltration
Runoff= Rainfall - Infiltration
Glacial Striations
Scratches and grooves on bedrock caused by glacial abrasion
Ultimate Base Level
Sea level; the lowest level to which stream erosion could lower the land
Sediment Transport
Sediment acquired by a stream is transported through the channel network along sections referred to as trunk streams
Bed Load
Sediment move along the bottom of a stream by moving water, or particles move along the ground surface by wind
Stratified Drift
Sediments deposited by glacial meltwater
Bars
Small-scale channel deposits
Infiltration
Soaks into the ground
Some important & well-known passes that are cols include St. Gothard Pass in the Swiss Alps, Tioga Pass in California's Sierra Nevada, and Berthoud Pass in the Colorado Rockies.
Some important & well-known passes that are cols include St. Gothard Pass in the Swiss Alps, Tioga Pass in California's Sierra Nevada, and Berthoud Pass in the Colorado Rockies.
Meandering Channels
Streams that transport much of their load in suspension generally move in sweeping bends called meanders
The 2015 Nepal earthquake (the Himalayan earthquake) which killed nearly 6,000 people and injured more than twice as many as of 30 April 2015, occurred at 11:56 NST on 25 April with a moment magnitude (Mw) of 7.8 or 8.1Ms and a maximum Mercalli Intensity of IX (Violent). Its epicenter was approximately 34 km (21 mi) east-southeast of Lamjung, Nepal, and its hypocenter was at a depth of approximately 15 km (9.3 mi) It was the most powerful disaster to strike Nepal since the 1934 Nepal-Bihar earthquake. Some casualties have also been reported in the adjoining areas of India, China, and Bangladesh. India responded with Operation Maitri for rescue and relief in Nepal by its armed forces and also evacuated Indian and foreign citizens from Nepal. The earthquake triggered an avalanche on Mount Everest, killing at least 19, making it the deadliest day on the mountain in history. It triggered another huge avalanche in Langtang valley, where 250 are now missing. Centuries-old buildings were destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including some at the Kathmandu Durbar Square, the Patan Durbar Square and the Bhaktapur Durbar Square. Nepal's government has declared three days of mourning after the quake. Geophysicists and other experts had warned for decades that Nepal was vulnerable to a deadly earthquake, particularly because of its geology, urbanization, and architecture. Continued aftershocks occurred throughout Nepal, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST. The country is at continued risk of landslides as well.
The 2015 Nepal earthquake (the Himalayan earthquake) which killed nearly 6,000 people and injured more than twice as many as of 30 April 2015, occurred at 11:56 NST on 25 April with a moment magnitude (Mw) of 7.8 or 8.1Ms and a maximum Mercalli Intensity of IX (Violent). Its epicenter was approximately 34 km (21 mi) east-southeast of Lamjung, Nepal, and its hypocenter was at a depth of approximately 15 km (9.3 mi) It was the most powerful disaster to strike Nepal since the 1934 Nepal-Bihar earthquake. Some casualties have also been reported in the adjoining areas of India, China, and Bangladesh. India responded with Operation Maitri for rescue and relief in Nepal by its armed forces and also evacuated Indian and foreign citizens from Nepal. The earthquake triggered an avalanche on Mount Everest, killing at least 19, making it the deadliest day on the mountain in history. It triggered another huge avalanche in Langtang valley, where 250 are now missing. Centuries-old buildings were destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including some at the Kathmandu Durbar Square, the Patan Durbar Square and the Bhaktapur Durbar Square. Nepal's government has declared three days of mourning after the quake. Geophysicists and other experts had warned for decades that Nepal was vulnerable to a deadly earthquake, particularly because of its geology, urbanization, and architecture. Continued aftershocks occurred throughout Nepal, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST. The country is at continued risk of landslides as well.
The Great Lakes were created by glacial erosion during the Ice Age.
The Great Lakes were created by glacial erosion during the Ice Age.
Lake Agassiz
The Largest Lake to form during the Ice Age in North America
The Mississippi River has the largest drainage basin in North America, collecting and carrying 40% of the flow in the U.S.
The Mississippi River has the largest drainage basin in North America, collecting and carrying 40% of the flow in the U.S.
The Ross and Ronne-Fichner Ice Shelves are the largest, with the Ross Ice Shelf covering an area approximately the size of Texas
The Ross and Ronne-Fichner Ice Shelves are the largest, with the Ross Ice Shelf covering an area approximately the size of Texas
The ability of a stream to erode and transport material is directly related to its flow velocity.
The ability of a stream to erode and transport material is directly related to its flow velocity.
Cut Bank
The area of active erosion on the outside of a meander
Glacial Budget
The balance, or lack of balance, between ice formation at the upper end of a glacier and ice loss in the zone of wastage
Head (Headwaters)
The beginning or a source area for a stream
The coastal wetlands of Louisiana are disappearing at an alarming rate-accounting for 80% of the wetland loss in the lower 48 states.
The coastal wetlands of Louisiana are disappearing at an alarming rate-accounting for 80% of the wetland loss in the lower 48 states.
Evapotranspiration
The combined effect of evaporation and transpiration
Secondary Enrichment
The concentration of minor amounts of metals that are scattered through unweathered rock into economically valuable concentrations by weathering processes
Gradient
The slope of a stream, generally expressed as the vertical drop over a fixed distance
Settling Velocity
The speed at which a particle falls through a still fluid
Nuclear Fission
The splitting of atomic nuclei into smaller nuclei, causing neutrons to be emitted and heat energy to be released
Paleoclimatology
The study of ancient climates; the study of climate and climate change prior to the period of instrumental records using proxy data
Wetted Perimeter
The total distance in a linear cross-section of a stream that is in contact with water
Greenhouse Effect
The transmission of short-wave solar radiation by the atmosphere coupled with the selective absorption of longer-wavelength terrestrial radiation, especially by water vapor and carbon dioxide, resulting in warming of the atmosphere
Hydrologic Cycle
The unending circulation of Earth's water supply. The cycle is powered by energy from the Sun and is characterized by continuous exchanges of water among the oceans, the atmosphere, and the continents
Water Table
The upper level of the saturated zone of groundwater
Zone of Fracture
The upper portion of a glacier consisting of brittle ice
This last process relies on the property that as water changes state from liquid to solid, heat (termed latent heat of fusion) is released.
This last process relies on the property that as water changes state from liquid to solid, heat (termed latent heat of fusion) is released.
Rills
Tiny channels formed by threads of current developed by thin, unconfined flow
Aerosol
Tiny solid and liquid particle suspended in the atmosohere
Truncated Spurs
Triangular-shaped cliffs produced when spurs of land that extend into a valley are removed by the great erosional force of a valley glacier
Alluvium
Unconsolidated sediment deposited by a stream
Till
Unsorted sediment deposited directly by a glacier
Ore
Usually a useful matallic mineral that can be mined at a profit. The term is also applied to certain nonmetallic minerals such as fluorite and sulfur
Climate-Feedback Mechanism
Various outcomes that may result when one of this complex interactive physical system's elements is altered
Vf= Adb * Runoff
Vf= Adb * Runoff
Calving
Wastage of a glacier that occurs when large pieces of ice break into the water
Erosional Floodplain
When a river erodes laterally and creates a floodplain
Grounded
When the ice shelf "touches bottom" in shallow water
Transpiration
The release of water vapor to the atmosphere by plants
Quarrying
The removal of blocks from the bed of the channel
Norway, British Columbia, Greenland, New Zealand, Chile, and Alaska all have coastlines characterized by fjords.
Norway, British Columbia, Greenland, New Zealand, Chile, and Alaska all have coastlines characterized by fjords.
Flash Floods
Occur with little warning and are potentially deadly because they produce rapid rises in water levels and an have devastating flow velocities
Biomass
Organic material that's renewable energy derived from trees, crops, and waste. Examples include biofuels such as ethanol and biodiesel, as well as biogas, which is methane recovered from landfills
Hydrograph
Plots discharge (or stage) at a gauging station over time
Presently each of Earth's polar regions supports an ice sheet-Greenland in the Northern Hemisphere and Antarctica in the Southern Hemisphere
Presently each of Earth's polar regions supports an ice sheet-Greenland in the Northern Hemisphere and Antarctica in the Southern Hemisphere
Depositional Floodplain
Produced by major fluctuations in condition, such as changes in base level or climate
The earthquake occurred on 25 April 2015 at 11:56 a.m. NST (06:11:26 UTC) at a depth of approximately 15 km (9.3 mi) (which is considered shallow and therefore more damaging than quakes that originate deeper in the ground),[21] with its epicenter approximately 34 km (21 mi) east-southeast of Lamjung, Nepal, lasting approximately twenty seconds.[22] The earthquake was initially reported as 7.5 Mw by the United States Geological Survey (USGS) before it was quickly upgraded to 7.9 Mw and finally downgraded to 7.8 Mw. The China Earthquake Networks Center (CENC) reported the earthquake's magnitude to be 8.1 Ms. The India Meteorological Department (IMD) said two powerful quakes were registered in Nepal at 06:11 UTC and 06:45 UTC. The first quake measured 7.9 Mw and its epicenter was identified at a distance of 80 km to the northwest of the capital Kathmandu. The second earthquake was somewhat less powerful at 6.6 Mw. The seismic focus lay at a depth of 10 km (6.2 mi) below the earth's surface. Bharatpur was the nearest major city to the main earthquake, 53 km (33 mi) from the epicenter. The second earthquake occurred 81 km (50 mi) northwest of Kathmandu, the capital of Nepal. Over thirty-five aftershocks of magnitude 4.5 Mw or greater occurred in the day following the initial earthquake, including the one of magnitude 6.6 Mw.[23] According to the USGS, the temblor was caused by a sudden thrust, or release of built-up stress, along the major fault line where the Indian Plate, carrying India, is slowly diving underneath the Eurasian Plate, carrying much of Europe and Asia.[21] Kathmandu, situated on a block of crust approximately 120 km (75 miles) wide and 60 km (37 miles) long, reportedly shifted 3 m (10 ft) to the south in just 30 seconds. The risk of a large earthquake was well known beforehand. In 2013, in an interview with seismologist Vinod Kumar Gaur, The Hindu quoted him as saying, "Calculations show that there is sufficient accumulated energy [in the MFT], now to produce an 8 magnitude earthquake. I cannot say when. It may not happen tomorrow, but it could possibly happen sometime this century, or wait longer to produce a much larger one."According to Brian Tucker, founder of a nonprofit organisation devoted to reducing casualties from natural disasters, some government officials had expressed confidence that such an earthquake would not occur again. Tucker recounted a conversation he had had with a government official in the 1990s who said, "We don't have to worry about earthquakes anymore, because we already had an earthquake"; the previous earthquake to which he referred occurred in 1934.
The earthquake occurred on 25 April 2015 at 11:56 a.m. NST (06:11:26 UTC) at a depth of approximately 15 km (9.3 mi) (which is considered shallow and therefore more damaging than quakes that originate deeper in the ground),[21] with its epicenter approximately 34 km (21 mi) east-southeast of Lamjung, Nepal, lasting approximately twenty seconds.[22] The earthquake was initially reported as 7.5 Mw by the United States Geological Survey (USGS) before it was quickly upgraded to 7.9 Mw and finally downgraded to 7.8 Mw. The China Earthquake Networks Center (CENC) reported the earthquake's magnitude to be 8.1 Ms. The India Meteorological Department (IMD) said two powerful quakes were registered in Nepal at 06:11 UTC and 06:45 UTC. The first quake measured 7.9 Mw and its epicenter was identified at a distance of 80 km to the northwest of the capital Kathmandu. The second earthquake was somewhat less powerful at 6.6 Mw. The seismic focus lay at a depth of 10 km (6.2 mi) below the earth's surface. Bharatpur was the nearest major city to the main earthquake, 53 km (33 mi) from the epicenter. The second earthquake occurred 81 km (50 mi) northwest of Kathmandu, the capital of Nepal. Over thirty-five aftershocks of magnitude 4.5 Mw or greater occurred in the day following the initial earthquake, including the one of magnitude 6.6 Mw.[23] According to the USGS, the temblor was caused by a sudden thrust, or release of built-up stress, along the major fault line where the Indian Plate, carrying India, is slowly diving underneath the Eurasian Plate, carrying much of Europe and Asia.[21] Kathmandu, situated on a block of crust approximately 120 km (75 miles) wide and 60 km (37 miles) long, reportedly shifted 3 m (10 ft) to the south in just 30 seconds.[24] The risk of a large earthquake was well known beforehand. In 2013, in an interview with seismologist Vinod Kumar Gaur, The Hindu quoted him as saying, "Calculations show that there is sufficient accumulated energy [in the MFT], now to produce an 8 magnitude earthquake. I cannot say when. It may not happen tomorrow, but it could possibly happen sometime this century, or wait longer to produce a much larger one."[25] According to Brian Tucker, founder of a nonprofit organisation devoted to reducing casualties from natural disasters, some government officials had expressed confidence that such an earthquake would not occur again. Tucker recounted a conversation he had had with a government official in the 1990s who said, "We don't have to worry about earthquakes anymore, because we already had an earthquake"; the previous earthquake to which he referred occurred in 1934.[26]
Terminal Moraine
The end moraine that marks the farthest advance of a glacier
Headward Erosion
The extension upslope of the head of a valley due to erosion
Floodplain
The flat, low-lying portion of a stream valley subject to periodic inundation
The flow of the Amazon account for about 15% of all the fresh water that flows into the oceans
The flow of the Amazon account for about 15% of all the fresh water that flows into the oceans
Abrasion
The grinding and scraping of a rock surface by the friction and impact of rock particles carried by water, wind, and ice
Stage
The height of the water surface relative to a fixed reference point
Hydrothermal Solutions
The hot, watery solution that escapes from a mass of magma during the latter stages of crystallization. Such solutions may alter the surrounding country rock and are frequently the source of significant ore deposits
Drainage Basin (Watershed)
The land area that contributes water to be a stream
Stratosphere
The layer of the earth's atmosphere above the troposphere, extending to about 32 miles (50 km) above the earth's surface (the lower boundary of the mesosphere).
Base Level
The level below which a stream cannot erode
Local (Temporary) Base Levels
The level of a lake, resistant rock layer, or any other base level that stands above sea level
Snowline
The lower limit of perennial snow
Troposphere
The lowest region of the atmosphere, extending from the earth's surface to a height of about 3.7-6.2 miles (6-10 km), which is the lower boundary of the stratosphere.
Capacity
The max. load of sold particles a stream can transport per unit time
Flow
The movement of glacial ice
Laminar Flow
The movement of water particles in straight-line paths that are parallel to the channel. The water particles move downstream without mixing.
Zone of Wastage
The part of a glacier beyond the snowline, where annually there is a new loss of ice
Zone of Accumulation
The part of a glacier that is characterized by snow accumulation and ice formation. The outer limit of this zone is the snowline
Mouth
The point downstream where a river empties into another stream or water body
Reservoir Rock
The porous, permeable portion of an oil trap that yields oil and gas
Dissolved Load
The portion of a stream's load that is carried in solution
Abrassion
The process by which the bed and banks of a bedrock channel are ceaselessly bombarded by particles carried into the flow
Quarternary Period
The recent period on the geologic time scale. It began about 2.6 million years ago and extends to the present
Thermosphere
The region of the atmosphere above the mesosphere and below the height at which the atmosphere ceases to have the properties of a continuous medium. The thermosphere is characterized throughout by an increase in temperature with height.
Mesosphere
The region of the earth's atmosphere above the stratosphere and below the thermosphere, between about 30 and 50 miles (50 and 80 km) in altitude.
