GEOGRAPHY 132 EXAM 2 STUDY GUIDE
∙ Karst landforms are those in a region with primarily carbonate rock (such as limestone) which is dissolved by solution processes in chemical weathering when rain seeps into the rock
∙ Common features are sinkholes, caves, disappearing/underground streams, karst valleys, and cockpit/tower/rill karst
∙ Conditions for karst are 80% carbonate in limestone, complex joints (lots of cracks) in bedrock, and an aerated zone
∙ Major karst regions are found in southeast Asia, like China and Thailand ∙ There are 2 types of sinkholes, collapse and solution. Collapse sinkholes form when acidic groundwater dissolves bedrock and causes the surface rock to fall down, and they are not visible on surface until the surface rock collapses. Solution sinkholes are more common, and they form when slightly acidic water eats away at the surface slowly until a depression forms.
∙ Disappearing streams occur when streams run into sinkholes and disappear underground before emerging elsewhere. They are often mapped by putting dye packets in the streams and noting where the dye lets
∙ There are 3 types of karst: cockpit, tower, and rill. Cockpit karst consists of a landscape with many interlocking sinkholes, and can be found in Jamaica and Puerto Rico. Tower karst is karst with towers that can be as high as 600 feet and only occurs in wet tropical areas with thick limestone beds; it is common in China. Rill karst consists of many small channels that have been weathered into the rock and forms in areas with very pure limestone. Caving and rock climbing are popular activities in karst areas.
∙ Caves form when water dissolves CaCO3 and forms carbonic acid, which wears away the rock and forms an opening which becomes a cave ∙ Cave features are called speleothems and they include stalactites, which hang from the roof, stalagmites, which stick up from the floor, and columns, which happen when stalactites and stalagmites connect. These features form when the water that wore away the rock hits air again and redeposits calcite. This process is called reprecipitation, and is the opposite of dissolution
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Hydrologic Cycle and Water Budgets
∙ Water quality and quantity matters because we need water to live and do anything. Quality matters because the water needs to be good enough to be useful, and quantity matters because we need enough to be able to get everything done
∙ Recently, quantity is decreasing as a result of draining aquifers that have stored water for thousands of years and are not being replenished. This could be disastrous when the aquifers are completely depleted because we do not know what we’re going to do to sustain agriculture. Quality is also depleting as more and more fertilizers and chemicals are released into water and carried off in streams
∙ The hydrologic cycle is the movement of water through the atmosphere and around the earth by evaporating, being precipitated, and moving around in rivers, streams, and the ocean If you want to learn more check out What does bernini's david sculpture represent?
∙ Terrestrial components of the hydrologic cycle are rivers and lakes, atmospheric components are clouds and rain, and subterranean components are groundwater and aquifers
∙ Groundwater is water that goes down below the soil and is stored there until there is not enough precipitation. Surplus occurs when there is precipitation in excess of an area’s need for water. Runoff occurs with a surplus when there has been too much extra water for the ground to store it all and some of it runs back off into rivers and streams
∙ Soil-water budgets are used to determine the amount of water available to plants and other organisms in an area and are based on the amount of precipitation an area typically receives, the amount of organisms in the area that need water, and the amount of water that can be stored below ground. They help governments plan how to distribute water resources If you want to learn more check out What is the meaning of paraphilia in psychology?
∙ PRECIP in the soil water budget represents the amount of precipitation received
∙ POTET represents the amount of evapotranspiration (evaporation and transpiration) by all the plants that an area could perform if it had enough water to do so. It is determines by putting water in an evaporation pan and seeing how long it takes to evaporate OR by using a lysimeter to isolate a block of water and measure incoming & outgoing water
∙ ACTET represents the actual amount of evapotranspiration carried out in the area. If precipitation is high enough or if there is enough water in storage, it will be equal to POTET. It is dependent on temperature and relative humidity We also discuss several other topics like How many unsafe abortions happen a year?
∙ DEFIC represents a deficit, when there is not enough water for all the evapotranspiration that is possible to occur. It is the amount of POTET that is not supplied by the water supply
∙ SURPL represents a surplus, when there is more than enough water for POTET to be satisfied. It is the amount that is neither used in evapotranspiration nor stored in the soil
∙ ΔSTRGE represents the change in the amount of water in storage underground. It can be depleted in times of insufficient precipitation and recharged in times when precipitation is plenty
∙ Utilization of soil water occurs when POTET exceeds precipitation and plants must use water stored in soil to hydrate themselves
∙ In dry climates, POTET will often exceed ACTET. In addition, warm climates will have a higher POTET than cold climates
∙ Groundwater is water contained in soil & rocks below the root zone & is tied to surface supply through pores in the soil. There is 70x as much groundwater as surface fresh water, and it was all taken up by aquifers a long time ago and stored thereIf you want to learn more check out Is there a significant difference in your and your parents’ way of living, values, or tastes?
∙ Groundwater is good drinking water because it is naturally purified when it runs through the soil, but threats to groundwater as a source are overuse and pollution. Once groundwater is contaminated, it is essentially done for, and once the aquifer from which it is being drawn runs out, there is no way to get any more
∙ Water coming underground first passes through the zone of aeration or “root layer”, which is the unsaturated zone between the surface and the water table. The water then reaches the zone of saturation, where all the pore space in the soil is completely filled with water. The very top of the zone of saturation is called the water table
∙ Aquifers are areas of the ground made up of a material with high permeability, such as limestone, where water is stored. Aquifers are able to store water because of the existence of aquacludes, layers made of material that is impermeable and thus prevents water from passing through. Aquifers work by storing water inside the ground until it is pulled up via a well or other method
∙ There are 2 types of aquifer, confined and unconfined. Unconfined aquifers have the permeable layer on the top and the aquaclude on the bottom, and water must be pumped from these aquifers. The recharge area, or area where water comes back into the aquifer, is the entire area above the permeable layer for unconfined aquifers (very large). Confined aquifers are bounded by aquifers both below and above, and they do not need to be pumped because the water is pressurized by its own weight and rises on its own. Confined aquifers have very small recharge area and are therefore more susceptible to pollution Don't forget about the age old question of Where in the roots of bean plants do nitrogen fixing bacteria live?
∙ Potentiometric surface is the level to which water in a confined aquifer rises above the water table, and artesian wells are sites where the water in a confined aquifer flows all the way to the surface as a result of the pressure
∙ Fossil water is water that entered an aquifer a long time ago and has been stored for thousands of years, and it is not being recharged today ∙ There are 2 types of streams with regards to interaction with groundwater, influent and effluent. Effluent streams take in water from the surrounding ground, and influent streams lose water to the surrounding ground ∙ Groundwater mining is when water is taken out of the ground much faster than it is replenished by nature, and it takes a long time to renew. This can form a cone of depression, which is a local depression at the site where groundwater is drained, or a collapsing aquifer, in which all water is moved and the soil loses its porosity, making it unable to hold water anymore, and the land subsides. Near oceans, saltwater encroachment can also occur, and this is when too much groundwater is removed near a coastline and is replaced by saltwater, rendering the aquifer unusable by humans ∙ The Ogallala Aquifer is a large aquifer extending from South Dakota to Texas from which 14 million acres of land draw their irrigation water. Since 1950, water levels in the Ogallala Aquifer have dropped 100 feet and it is likely to run out soon because the water is very old and not being replenished quickly enough. We have no clue what we’re going to do when it runs out
∙ Pollution in groundwater can come from two types of sources: point sources, or single locations, and non-point sources, or broad areas. Once groundwater is polluted, it is extremely difficult and expensive to clean so it is best to avoid polluting it in the first place
Soil Characteristics and Properties
∙ Soil is composed of organic material and weathered rock, and is used as a medium for plant growth. Soil is important because without it there would be no life; we need it to grow the plants that produce oxygen and feed us, as well as feeding the other animals we eat
∙ The 2 main branches of soil science are edaphology, which is the study of soil as a medium for plant growth, and pedology, which is the study of the origin, classification, distribution, and description of soil
∙ Soils are characterized by numerous factors, such as color, moisture, chemistry, mineralogy, and structure
∙ Soil can take anywhere from centuries to millennia to develop, and there are several factors that can affect its formation.
∙ Its parent material can affect its formation because the parent material can be either weathered bedrock (regolith) at its location or weathered materials moved in from another location and deposited.
∙ Topography can also affect soil formation. In the northern hemisphere, north facing slopes are cooler and wetter than south-facing slopes, and east-facing slopes will be cooler when the morning sun shines, as opposed to west-facing slopes, which will be warmer as the afternoon sun shines.
∙ Climate also affects soil formation because moisture, evaporation, and temperature determine the chemical reactions and organic activity, and soils can be very old products of past climates.
∙ Biology is also important because vegetation, animal activity, and bacterial activity all affect the organic content of the soil. Additionally, the type of vegetation can alter the chemistry of the soil. Bioturbation is the process by which all animals and plants turn soil over
∙ Soil formation can also be affected by human activities such as altering soil on a very large scale and mechanized agriculture
∙ Soil surveys are county-level soil maps for the whole US designed by the NRCS-USDA, and they are available online. Soil profiles are unique cross sections from the surface of soil to the deepest extent of plant roots, and they provide the basis for classifying soils. A pedon is a hexagonal column of soil measuring 1-10 square meters, and is the basic mapping unit for soil. A polypedon is a group of multiple pedons together
∙ Soil profiles are composed of several horizons: O, A, E, B, C, and R. The O horizon is the top layer and is named O after its organic composition. It contains plant and animal litter deposited on the surface, as well as humus, which is a mix of decomposed organic material important for retaining nutrients. The A horizon is the second down, rich in organic content, and darker than the lower horizons. It is often disrupted by humans, and it grades into the next horizon down, the E horizon. The E horizon is below the A
horizon and is lighter in color, and is named for being the zone of eluviation, which is the leaching of materials. Silicate clays, iron oxides, and aluminum oxides are leached down from this layer to the lower horizons by water. Below the E horizon is the B horizon, which is darker, and it is the zone of illuviation, which is the deposition of leached materials. The clays and oxides from the E horizon are deposited here. Below the B horizon is the C horizon, which is the regolith (weathered parent material). The C horizon is outside of biological influence and is often cemented. Below the C horizon, at the very bottom, is the R horizon, composed of unconsolidated rock (bedrock).
∙ The solum is the name of the A, E, and B horizons together and is the zone of active soil formation.
∙ Soil color often suggests the chemicals present in the soil and is usually the most obvious property. Soil contains a mixture of different particle sizes, and the proportion of particle sizes determines the texture of the soil. All particles less than 2mm are considered part of the soil. Soil texture is important for determining water retention, and loam is a type of soil texture that is a balance between sand, silt, and clay that is good for plant growth. Soil structure is the arrangement of soil particles. A ped is the smallest natural lump or cluster of particles, and the shape of the ped determines the soil structure. Structure can be granular, platy, blocky, or prismatic/columnar. The consistence of soil is the cohesion of its particles and their resistance to breaking. Plasticity is how plastic the soil is, friability is how crumbly it is, and brittleness is whether or not it breaks. Porosity is the pore space within the soil. It controls the movement of water through the soil, and it is improved by biotic action, such as worms and gophers.
∙ The 3 types of moisture within soil are gravitational, capillary, and hydroscopic. Gravitational water is water that moves down through the soil. Capillary water is water that pulls itself through the pores of the soil. Hygroscopic water is water that clings to the outside of soil particles.
∙ The pores in soil contain air, water, or a combination of both. Soil solution is the water in the pores of soil, and a medium for the chemical reactions within soil. Colloids are particles of clay or humus with negative charge that attract positively-charged cations. The cation exchange capacity (CEC) measures the ability of a colloid to exchange nutrients. More colloids means a higher CEC, which results in higher soil fertility.
∙ Soil high in H+ ions stimulates acid formation, making the soil acidic, while soil high in base ions such as Ca+ or Na+ stimulates base formation, making it alkaline. Soils with a pH below 7 are acidic, soils with a pH above 7 are basic/alkaline, and soils with a pH of 7 are neutral.
∙ Because there are so many different types of soils, there is a taxonomy used to classify them. Soils are classified taxonomically, from largest to smallest, in orders, suborders, great groups, subgroups, families, and series. The taxonomy relies on the identification of horizons and distinguishing features.
∙ Soils are linked to climate regions because the different types are largely the result of climate and vegetation, so the different soil types align roughly with earth’s biomes.
∙ The 12 main soil orders are oxisols, aridisols, mollisols, alfisols, ultisols, spodosols, entisols, inceptisols, gelisols, andisols, vertisols, and histosols. ∙ Oxisols are tropical soils that can be found in warm, tropical environments. They are generally old and red in color, and are also low in organic matter. Despite being in an environment rich in vegetation, the nutrients are all contained within the plants themselves, so once they are gone, the soil is very poor. Oxisols can experience laterization, which occurs when almost all iron and minerals are leached from the surface and deposited in the lower A or B horizons
∙ Aridisols are dry soils found in arid, desert climates. They are light in color and have a lack of surface vegetation and organic matter. There is little water in these climates, so the soils are not leached, which allows salt and carbonates to build up in the soils. This makes them bad for agriculture
∙ Mollisols are grassland soils that are soft and crumbly with high fertility, making them good for agriculture. They have dark surface layers rich in organic material. The fertility is created by a combination of high organic and low leaching due to moderate rainfall, but occasionally, because of the low leaching, a carbonate layer called caliche can build up in the soil
∙ Alfisols are moderately weathered soils in temperate forest areas, and they are the most widespread. They have moderate to high reserves of basic cations, so they hold onto nutrients well and are fertile. Fertility of individual soils is dependent on the moisture level in their particular environments
∙ Ultisols are highly weathered soils in subtropical forests, and are often considered degenerated alfisols. They are found in warm and humid climates with moist weathering conditions. A high level of precipitation causes eluvial leaching and lowered fertility, and the soil gets a red color from iron
∙ Spodosols are soils from northern coniferous forests that are found in cold, forested, moisture-rich regions. The A horizon of spodosols is sandy and leached of clays, while the B horizon consists of illuviated organic matter and iron and aluminum oxides. For agriculture to be possible in this soil, a limestone amendment is needed to increase the pH. This process is known as liming. The process by which soil is acidified is known as podsolization
∙ Entisols are recently formed soils which are underdeveloped and have a notable lack of development of vertical horizons. There is either too much or too little water in the area for these soils to develop properly, and they are poor for agriculture
∙ Inceptisols are weakly-developed baby soils where weathering has only just begun. They are infertile and you, and found in moist areas, and thus have mostly eluvial processes and little illuviation
∙ Gelisols are cold, frozen soils underlain by permafrost in periglacial landscapes. Below-freezing temperatures make the development of soil slow and disturbance of the soil long-lasting. In addition, it causes cryoturbation,
which is when freeze-thaw action makes the horizons mix together. Gelisols are generally low-developed
∙ Andisols are found in areas of volcanic activity, and are derived from volcanic ash and glass. They have a high cation exchange capacity, high water holding capacity, and good fertility
∙ Vertisols are expandable clay soils with over 30% swelling clays. Soil moisture is highly variable throughout the year, and they are found in tropical and subtropical climates with a distinct dry season after a rainy season. Spatial extent is very limited
∙ Histosols are thick accumulations of organic matter, and can be found in beds of former lakes where water is gradually replaced by organic material. They are found in bogs and other low-lying areas where water accumulates. Histosol bricks are used as fuel
Elemental Cycles and Soil Conservation
∙ The elements in living matter are carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur
∙ Nutrient cycling details the way these elements move through the spheres of the earth and biosphere specifically to reach the organisms that need them ∙ Water travels through the water cycle by evaporating from bodies of water at
the surface, condensing into clouds in the atmosphere, and falling back down to earth as precipitation, which can either go into the earth and be stores as groundwater until it is used or flow back into an above-ground body of water and evaporate again
∙ Carbon travels through the carbon cycle by being taken up by plants when it is stored in soil, then being taken in by organisms when they eat plants, then given off by organisms in the form of waste, death and resulting decomposition, and carbon dioxide, then having that carbon dioxide be taken in by plants and the carbon from waste and dead organisms go back into the soil
∙ Photosynthesis is the process by which plants create their own food. They take in energy from the sun, along with water and nutrients from the soil, and carbon dioxide, and produce energy within themselves as well as giving off oxygen that animals need to breathe
∙ We care about carbon storage and release because carbon is the building block of all life. All living beings are made up of carbon, and the microorganisms that break down materials also need carbon to function. In addition, carbon is a significant factor in most greenhouses gases, which play an important role in causing climate change
∙ Nitrogen is the most abundant element in the atmosphere, and we need it to live, but we can’t breathe it in, so we have to get it from our food instead. Nitrogen in the atmosphere moves down into the soil and is converted from nitrogen to ammonium by bacteria. Other bacteria then convert the ammonium to nitrates and nitrites, which are taken up by plants and are in turn taken up by us when we eat the plants or whatever animals ate the plants
∙ When there is too much nitrogen, excess nitrogen gets run off with water and acidifies soil, preventing plants from growing. This must be corrected by adding limestone or chalk to the soil (liming) to get the pH back down. If the pH gets too low, however, more nitrogen must be added again, and the process repeats itself over and over. Another problem caused by excess nitrogen is algae blooms that occur when there is too much nitrogen in the water supply. Algae blooms take all the oxygen in the water and create anoxic zones where fish and other organisms can no longer live
∙ Soil is not a renewable resource because it takes an extremely long time to be created and can become devoid of usefulness much more quickly than it will be replaced
∙ The best method for sustaining soil is no-till & cover crops, which is when you grow a crop in winter to increase biomass so you don’t need to use as much fertilizer. It is also good to reintegrate wetland areas so they will filter out excess nitrogen before it reaches the river
Oceans and Coastal Processes
∙ Coastlines are the edges of continents that border bodies of water, and they are also sites of energy exchange and sediment transport. 40% of the world’s population lives within 100 km of coastlines because they are important for food, water, travel, and commerce
∙ Oceans are considered a final frontier for science because we know very little about them and we are still discovering new things in the ocean all the time. We actually know more about the moon than we know about our oceans
∙ The ocean is a solution, meaning it contains dissolved solids (solutes), and the solutes in the ocean are salts. The concentration of salts is the salinity, and while the salinity may change, the ratio of individual salts present does not change. The ocean contains many different salts, and these 7 elements make up 99% of seawater: chlorine, sodium, magnesium, sulfur, calcium, potassium, and bromine. The ocean also contains dissolved gases (such as carbon dioxide, nitrogen, and oxygen) and trace minerals at underwater hot spots
∙ The average salinity of the ocean is ~3.5%, but salinity varies depending on latitude. In hot areas, more water is being evaporated and leaving salt behind, so the water has higher salinity. The average pH of the ocean is 8.2, but it is decreasing as the ocean continues to absorb more carbon dioxide and becomes more acidic as a result
∙ Brine water is water with an average salinity that is greater than 3.5%. It can be found at brine lakes, deep pockets, and enclosed basins, such as the Red, Mediterranean, and Dead seas. Brackish water, on the other hand, is water with an average salinity less than 3.5%. Water is generally brackish near a land mass
∙ The inputs to coastal systems are solar energy, atmospheric winds, climatic regimes, coastal geomorphology, and human activities
∙ The littoral zone is the zone of interaction between the land and the sea, and these are the locations where energy is transferred between the sea and the land and where sediments are deposited and moved around between the two
∙ Mean sea level is based on the average tidal level recorded at a given location over many years, and it can change. For example, sea level is higher at the equator because spinning on its axis causes the earth to bulge in the middle. Mean sea level is an important measure because all elevations are based off it
∙ Tides are daily oscillations in sea level, and can range from very few to many meters. They are an energy agent for geomorphic change, and are also important for human activities because they determine the timing for important things like port entry for ships and fishing. They are caused by the gravitational pull of the moon and the sun (more the moon because it is closer) and come in the form of high (flood) and low (ebb) tides. In addition to the ocean, large lakes, such as Lake Superior, can also have tides
∙ There are 2 types of special tides, spring tides and neap tides. Spring tides occur during full and new moons when the sun and moon are aligned and are stronger than normal tides due to the gravitational forces of the sun and moon working together. Neap tides occur during first and third quarter moons and are weaker than regular tides due to the gravitational forces of the sun and moon working in different directions
∙ Waves are the movement of energy through water caused by the friction between wind and the ocean’s surface. Groups of waves are called wave trains, and wave trains are radiated outward from areas with stormy conditions. When two wave trains interact in the open ocean, it is known as interference. If they are going different directions, they can cancel each other out, but if they are going in the same direction, they can align and reinforce each other, creating a rogue wave
∙ There are 2 kinds of waves: transition and translation. Waves of transition can also be called waves of oscillation, and these are waves in which only energy moves, not mass. Waves in the open ocean are waves of transition. Waves of translation move mass along with the energy of the wave. Breaking waves at coasts and waves in rivers are both waves of translation
∙ Waves are created by friction from wind, and the movement occurs in swells, which transfer energy. Movement in swells is in a circle, and the size of the circular motion decreases with underwater depth
∙ The characteristics of a wave are wave length, which is the distance crest to crest or trough to trough; wave height, which is the distance crest to trough and determines potential energy; amplitude, which is the distance from the center of the wave to either crest or trough; and the wave period, which is its frequency (how often it occurs). When waves reach shallow water, their wavelengths are shortened
∙ Waves are active until half a wavelength underwater, and when they reach water that is the depth of half a wavelength, they touch bottom. At this point, the wavelengths get shorter and they turn into waves of translation, pushing the water and sediment. When the waves become too high and lose their stability, they collapse into breakers
∙ There are 2 types of breakers, plunging breakers and spilling breakers. Plunging breakers are found at steeper beaches while spilling breakers are found at gentler ones
∙ Waves exert a type of energy at the shore when they break called hydraulic pounding. Other forces enacted on the shore by waves are spray from the breaking waves, wich can travel as fast as 70 miles per hour, and abrasive tools like sand that are carried by waves (this is known as a suspended load). Waves can also force air into the cracks of a rock
∙ Wave refraction occurs when waves are bent around headlands and other protruding features. As a result, energy is concentrated on the headlands and dissipated in between. This process works to straighten coastlines over time
∙ Factors that affect wave action on the shore are changes in sea level, tides, storms, and tsunamis
Coastal Processes and Landforms
∙ Rip currents occur when backwash flows back out to sea directly in a concentrated column, and people often get caught in these and dragged pretty far out to sea. The method to escape one is not to swim back toward shore, but instead to swim parallel to shore until you are out of the current, then swim back
∙ Longshore currents, also known as littoral currents, move along parallel to the coast and are created by the swash (washing in) and backwash (washing out) of waves moving at angles to one another. They transport sand and other materials in a direction parallel to the beach in a process known as beach drift or littoral drift. They work to straighten coastlines naturally
∙ Tsunamis are seismic earthquakes that result from underground earthquakes or volcanic activity. They originate far out in the middle of the ocean and are characterized by having a very low height at sea, only around one meter, but a very long wavelength, up to 100 kilometers. Because the wavelength is so long, they often go unnoticed in the open ocean even if they do pass by boats. When they reach shallow water, wavelength shortens and the wave grows incredibly high, sometimes as tall as 50 feet. These huge waves cause large amounts of destruction and erosion, and the separate waves of tsunamis come about 10 minutes apart. Even though it is possible to know when an earthquake has occurred underwater, it is hard to know how fast a tsunami is travelling or how powerful it will be, so it is difficult to predict them and prevent damage
∙ The 2 types of coastal landforms are erosional and depositional. Erosional landforms are the result of high energy and waves eroding the land. Depositional landforms are the result of low energy and waves depositing sediments
∙ Erosional landforms are rugged and steep, and they are found in tectonically active areas such as the Pacific coast of North and South America ∙ Terraces, wave-cute platforms, sea cliffs, sea caves, sea arches, and sea stacks are all erosional landforms. They are the result of differential erosion. Sea cliffs occur when waves undercut cliffs until they collapse. Wave-cut
platforms occur when waves cut horizontal benches in the tidal zone, then changes in sea level raise up benches where they become platforms or terraces separated by former sea cliffs
∙ Depositional landforms occur in areas of low relief with abundant sources of sediment that are not tectonically active, such as the Atlantic and Gulf coasts ∙ Larger particles being transported fall out of the water at higher velocities than smaller particles. When a river reaches a lake or ocean, velocity decreases and particles are deposited. Larger and denser particles are deposited first, so in this way, particles are sorted by size
∙ A beach is an area along the coast where sediment is in motion, and the type of sediment found at the beach varies by location. Beaches are made of regolith, usually sand, and the particle size of the sand on a beach is determined by the strength of the ocean’s waves at its location; bigger waves mean bigger particles. Some beaches are stable all year, while others vary seasonally. The second kind of beach has its sand eroded and moved offshore by winter storms, then get brought back in by smaller waves during the summer
∙ A barrier spit is a bar of sand that extends partially across the entrance to a bay. A barrier spit becomes a bay barrier, or baymouth spit, once it extends fully across the entrance to the bay, blocking the body of water inside and separating it from the rest of the ocean. This now blocked-off bay is called a lagoon. A barrier spit that extends from the coast to a sea stack or island is called a tombolo
∙ Barrier islands are long, narrow depositional features that form roughly parallel to the coast. They are usually made of sand, and they are also always moving toward the continent because of wind and overwash. They protect the mainland from storms
∙ Coral are simple marine invertebrates that secrete calcium carbonate and form a hard exoskeleton. They live in a symbiotic relationship with algae and thrive in warm environments, mostly in the tropics. They require very specific conditions in temperature, salinity, depth, etc. to stimulate growth
∙ Coral reefs are large structures of colonial corals, as opposed to solitary corals. They build on themselves over time, forming a biologically derived sedimentary rock, and they also often formed around volcanic islands, eventually forming an atoll
∙ Salt marshes are a type of coastal wetland that forms north of the 30th parallel in the northern hemisphere. They tend to form behind barrier beaches and spits, and contain salt tolerant, or halophytic , plants
∙ Mangrove swamps are coastal wetlands that occur south of the 30th parallel in the northern hemisphere, and their distribution is controlled by freezing conditions. These swamps occur when mangrove trees anchor their roots in sediment accumulations along tropical shorelines
Human Interactions with Oceans and Coasts
∙ As pollution increases, coral is threatened because it is less able to get the nutrients required, and additionally, the algae with which it is in a symbiotic
relationship is also affected, so the coral begins to fail. As the climate changes, coral begins to die, because coral can only live in very specific conditions. Once those conditions are no longer satisfied, the coral will be unable to live
∙ Development in coastal wetland areas shrinks the area of the actual wetland and forces many unique organisms out of their wetland homes, leaving them nowhere else to go because the wetland is the only place they can live. Climate change threatens the environmental balance found in the delicate wetland ecosystem, also making it impossible for some animals to continue living there
∙ Groins are walls that jut out into the ocean to prevent littoral drift from dragging all the sand away. Jetties are walls built on either side of a harbor ∙ We build seawalls to protect the beach and development behind it, but the ultimately end up getting rid of the beach because they reflect the wave energy back and increase the intensity of longshore drift. They also prevent sediment exchange between the beach and dunes, and concentrate energy at the ends of the wall. Construction of seawalls and groins causes the shoreline to change and destroys the beaches it was meant to save, and construction at one location usually affects other locations as well. In addition, the cost of “saving” the property usually exceeds the property’s value
∙ Beach replenishment is when sand is brought back in to refill the beach and return it to its original size. It is usually done to make the beach more attractive to tourists and increase profits. It may be successful in doing so, but the downfall is that it will have to be done again
∙ Dunes store sand that blows up from the beach and also serve as sand sources for the beach. They also protect barrier islands from overwash. When they are developed, they lose their ability to exchange sand with the beach and are no longer able to protect it from overwash. Over time, they can assist in depleting the beach