CHAPTER 10: Introduction to the Lithosphere


Summary of the Chapter

All landforms are composed of rocks or their weathered by products. Three main types of rocks can be identified on the Earth's surface: igneous, sedimentary and metamorphic. The rock cycle is a model that describes how various geological processes create, modify and influence rocks. The rock cycle suggests that all rocks originated from magma. This model also suggests that all rock types can be melted back into magma by tectonic forces that return rock to the mantle.

Time has a unique meaning to geoscientists. To a geoscientist time is not measured in seconds, minutes or days, but in eons, eras, periods, and epochs. Each one of these units measures time according to major geologic events that have occurred over the 4.6 billion years of Earth history. When a geoscientist mentions the Cretaceous we know that this is a time period that occurred between 65 to 144 million years ago.

Uniformitarianism is an important theory central to understanding in geology and geomorphology. This theory suggests that the continuing uniformity of existing geomorphic and geologic processes should be used as the intellectual framework for understanding the geologic history of the Earth. It rejects the idea that the landscape of the Earth is the result of catastrophic processes (e.g., the biblical flood).

Three types of rocks are recognized by geologists: igneous, sedimentary, and metamorphic. Igneous rocks are formed by the solidification of magma. This solidification can occur at or beneath the Earth's surface. Sedimentary rocks develop from the lithification of sediments or weather rock debris. Two general categories of sedimentary rocks exist: clastic and non-clastic. Metamorphic rocks are created by the alteration of existing rocks by intense heat or pressure.

Most rocks are composed of one or more minerals. The minerals that make up a rock can be produced by magma solidification (igneous rocks), sedimentation of weather rock debris (sedimentary rocks), or metamorphism (metamorphic rocks). Minerals are naturally occurring inorganic solids that have a crystalline and a unique chemical make-up. Geologists have discovered more than 2000 different types of minerals. The various types of minerals have been classified into nine groups.

Igneous rocks are produced by the crystallization of magma. This process can occur at the Earth's surface or beneath the ground. The type of igneous rocks that forms from solidification is controlled primarily by magma chemistry, temperature of crystallization, and rate of cooling. Four basic types of magma have been classified by geologists. This classification is based on chemistry.

Felsic magma contains relatively high quantities of sodium, aluminum, potassium, and silica. Its solidification produces granite, dacite, rhyolite, and granodiorite. Each of these rocks has a unique mineral composition and grain size.

Mafic magma is rich in calcium, iron, magnesium, and relatively poor in silica (between 45 to 52%). The rocks that are created from this magma include basalt and gabbro. These rocks are dominated by the minerals pyroxene, amphibole, and olivine.

Intermediate magma produces andesite and diorite. These rocks contain less silica (between 53 to 65%) and have a chemistry that is between felsic and mafic. Dominant minerals in these rocks include pyroxene, amphibole, and plagioclase feldspars.

Ultramafic igneous rocks contain relative low amounts of silica (< 45 %) and are dominated by the minerals olivine, calcium-rich plagioclase feldspars, and pyroxene. Peridotite is the most common ultramafic rock.

The Bowen reaction series is a model that suggests that the type of igneous rocks that form from felsic and mafic magma relies on the temperature of crystallization and the chemical composition of the originating magma. In this model, the formation of minerals starts with two different chemical sequences at high temperatures that eventually merge into a single series at cooler temperatures.

Three different types of sedimentary rocks exist. Most sedimentary rocks are of the clastic type. These rocks are formed by the lithification of weathered rock debris. Examples of clastic sedimentary rocks include sandstone, shale, and conglomerate. Identification of clastic sedimentary rocks is based on sediment particle type.

The other two types of sedimentary rocks are termed non-clastic. The first group of non-clastic sedimentary rocks form through the chemical precipitation and re-crystallization of elements and compounds in solution. Common precipitated sedimentary rocks include halite, gypsum, silcretes, ferricretes, limestone, and dolomite. The second group of non-clastic sedimentary rocks are created from the lithification of once living organisms. Some examples of these rocks are limestone, chalk, coal, and lignite.

Metamorphic rocks are created by the alteration of existing igneous or sedimentary rocks by heat, pressure, or through the chemical action of fluids. This alteration may cause simple chemical changes or structural modifications to the minerals found in the rock. Some common metamorphic rocks include slate, schist, gneiss, marble, and quartzite.

Heat begins to metamorphically change at a temperature of about 200 degrees Celsius. Heat can be applied to rocks through two processes: tectonic subduction and the intrusion of magma. Another name for this process is called thermal metamorphism.

Pressure alters rocks primarily by reorienting mineral crystals. Pressure usually acts in concert with heat. Pressure can be exerted on rocks through two processes: weight of overlying materials or through a variety of tectonic processes. Another name for this process is called dynamic metamorphism.

The alteration of rocks via the chemical action of fluids requires the presence of water and carbon dioxide. When water and carbon dioxide are mixed the fluid that is produced can alter rocks chemically by dissolving ions and causing chemical reactions. Another name for this process is called metosomatic metamorphism.

Internally the Earth is made up of several different layers. Above the outer core is the mantle. A number of different layers have been discovered in the mantle. On top of the mantle is the lithosphere. The surface of this layer is called the crust.

Through deep drilling and seismic evidence scientists have learned about the structure of the Earth. Structurally, the Earth is composed of a number of different layers. The outer most layer is called the crust and it sits on top of the mantle. The crust is a cool, rigid, and brittle layer. Two types of crust are classified: oceanic and continental. At the center of the Earth is the core, which is approximately 7000 kilometers in diameter. One interesting property of the crust is that it has the ability to float up and down. This process is called isostacy.

The core consists of two sub-layers: the solid inner core and the liquid outer core. These two layers are made of the same materials but exhibit slightly different physical properties. The inner core composed of nickel and iron and approximately 1220 kilometers in diameter. Surrounding the solid inner core is the outer core which is liquid in nature. This layer has a thickness of about 2250 kilometers.

Sitting on top of the core is the mantle. It is also composed of several different sub-layers. The upper mantle exists from the base of the crust downward to a depth of about 670 kilometers. It is thought to be composed of peridotite. Below the upper mantle is the lower mantle that extends from 670 to 2900 kilometers below the Earth's surface. This layer is hot and plastic. The top 100 to 200 kilometers of the upper mantle is called the asthenosphere.

One other layer often described by geologists is the lithosphere. The lithosphere consists of the crust and upper portion of the asthenosphere. This layer glides over the rest of the upper mantle.

The theory of plate tectonics is another important unifying idea in geology. Essentially, the theory suggests that the Earth's outer crust is composed of a number of plates that float on the mantle. This idea has been around for more than a century. However, scientists before 1960 could not explain the mechanism that moved the Earth's plates. This all changed when scientists discovered alternating patterns of rock magnetism in sea floor rocks. The patterns also correlated to an increasing age of the sea floor as a one moved away from mid-oceanic ridges. This discovery indicated that new oceanic crust was created at the mid-oceanic ridges. It was also discovered that oceanic crust was destroyed at the oceanic trenches. Many of these trenches are found in the Pacific Ocean basin bordering continental crust. Scientists have theorized that convection currents in the Earth's mantle cause the movement of the plates. This lecture concludes by showing how plate tectonics explains earthquakes, mountain building, volcanoes, and oceanic trenches.

Scientists have discovered that the Earth's crust consists of two basic types. Continental crust makes up the continents. Continental crust is mainly composed of granite, some metamorphic rocks, and sedimentary rocks. The age of these rocks varies from between 4 billion to 600 million years. The continental crust varies in thickness from between 10 to 70 kilometers. It is thickest under mountain ranges. The continents are actually quite complex geologic structures. At the center, exists a core of very old igneous and metamorphic rock that is called the basement of rock. Along and the margin of the basement rock are deposits of sedimentary rock that are called platforms. Together the basement rock and the platforms form a craton. Along the edges of the cratons are the continental margins and mountain belts. Rock mass is also added to the continents through a variety of intrusive and extrusive igneous processes.

Oceanic crust is created at the mid-oceanic ridges and destroyed at the oceanic trenches. Oceanic crust is relatively young age and is being created even today at mid-oceanic rift zones. Maximum age is about 200 million years. On average of oceanic crust is 7 km thick and mainly composed of the igneous rock basalt.

Mountains can be created by two processes on our planet. Some mountains owe their origin to vertical movements of rising magma at hot spots and along the margin of subduction zones. These processes produce isolated volcanic mountains. Many mountains occur as a linear group. The mechanism responsible for mountain ranges is tectonic plate collision. Colliding plates push sedimentary materials into an uplifted mass of rock that contains numerous folds and faults. The Earth has undergone a number of mountain building periods. For example, the Himalayas began the formation of about 45 million years ago. This orogeny is still going on today.

Geologists have developed a general model explain how most mountain ranges form. This model suggests that now and building involves three stages. The first stage involves the accumulation of sediments. In the second stage, tectonic collision causes rock deformation and crustal uplift. In the final stage, isostatic rebound continues to cause uplift despite erosion and causes the development of new mountain peaks through block faulting.

The Earth's crust shows evidence that large-scale tensional and compressional forces have deformed it. This deformation has created a variety of different folds and faults. A fold can be defined as a bend in rock that is due to compressional forces. Folds occur when the stress applied to rock does not exceed its internal strength and plastic deformation occurs. These bends are most obvious in sedimentary rocks that have beds of strata that were originally laid down horizontally. The simplest types of folds include monoclines, anticlines, and synclines. A recumbent fold is a more complex type of fold where one limb of the fold passes the vertical. Faults form when the stress applied to rock does exceed its internal strength. This condition causes the rock to rupture along a fault plane (area of weakness and fracture). A number of fault types are defined including normal, reverse, graben, horst, and strike-slip.

An earthquake is a sudden vibration of some portion of the lithosphere. It is caused by the quick release of potential energy through motion. Most earthquakes are the result of rock moving because of faults, tectonic subduction, or rifting. The Earth experiences about 150,000 significant tremors a year. But most of these events are just strong enough to be felt, only a few a cause large-scale damage. Earthquakes energy is transmitted to surround rock by seismic waves. Geologists have discovered that seismic motions actual consist of three different types waves: P-waves; S-waves, and surface waves. P-waves (by expansion and contraction of rock as the wave moves away from the focus) and S-waves (movement of rock perpendicular to the direction of seismic wave travel) travel through the body of rock. Surface waves produce a rolling or swaying motion on the surface of the effected rock.

The strength of earthquakes is usually measured relative to the Richter scale. This scale is logarithmic so each increase in magnitude represents 10 times more energy released by the quake.

Earthquakes cause considerable damage to the built environments of humans. However, the level of damage caused by an earthquake is not always related to its magnitude. The level of damage can be influence by time of occurrence, duration of the event, geology of the effected area, type of building construction, and population density. Earthquakes can also trigger several other damaging phenomena. This includes mass movements, fires, and tsunamis.

Volcanoes are openings on the Earth that release lava, tephra, and volcanic ash. Most of the Earth's volcanoes are located at or near tectonic subduction zones and the mid-ocean ridges. Some volcanoes are the result of lithospheric hots spots. Geologists have classified volcanoes into five different types. This classification is based on geomorphic form, magma chemistry, and the explosiveness of the eruption. The various types include: basalt plateau volcanoes, shield volcanoes, cinder cones, composite volcanoes, and explosive calderas.

The Earth's terrestrial surface or continents are made up of three types of landscapes: cratons; mountain belts, and the continental margins. All of the continents have the same construction. In their center is a nucleus very old rock basement rock that is made up of a mixture of igneous and metamorphic rocks. The exposed top of this feature is called shield. Large areas of basement rock are covered by relative flat sedimentary strata called the platform. Together the platform and basement rock form a craton. Some continental masses have several cratons that are separated from each other by mountain belts. Most of the continental mountain belts are found along the edge of the cratons. Mountain belts are formed when tectonic forces squish marine sedimentary deposits to the edges of the continents. This squishing process causes the sedimentary layers to become folded and faulted and their elevation increases to form mountains. Between the mountain belts and the ocean basins is the continental margin. Much of this continental surface is located below sea-level. The continental margin is made up three distinct landform types: the continental shelf; the continental slope; and the continental rise.

The other major topographic feature of the Earth is the ocean basins. The ocean basins are made up of relatively young basaltic volcanic rock that was released from fissures along the mid-ocean ridge. Oceanic crust is returned to the mantle at the subduction zones found along the continental margins. The ocean basins are not featureless. Some of features found here include the ocean floor, mid-oceanic ridges, ocean trenches, and numerous volcanoes (many of which form islands).

Geologists and geomorphologists recognize four basic types of landforms: structural landforms; weathering landforms; erosional landforms; and depositional landforms. Landforms and the geomorphic processes that create them are uniquely interrelated. Not only do the actions of geomorphological processes shape the landscape, landscape also determines which processes occur and at what rates they occur.

Weathering is the breakdown and alteration of rocks and minerals at or near the Earth's surface. The end products of weathering are the breakdown of a single mass into two or more smaller masses, the removal of atoms or molecules from the weathered surface, and the addition of certain atoms and molecules to the weathered surface. The products of weathering are a major source of sediments for the geomorphic processes of erosion and deposition. Rock and mineral weathering can be the result of a number of physical, chemical and biological processes. Physical weathering involves the disintegration of material by mechanical stress and rupture. Processes that can result in physical weathering include abrasion, crystallization, thermal insolation, wetting and drying and pressure release. Chemical weathering results from the chemical alteration of rock and minerals. The most common chemical weathering processes are hydrolysis, oxidation, reduction, hydration, carbonation, and solution. Finally, biological weathering involves the breakdown or rock and minerals through chemical and/or physical agents of an organism. A number of processes involved in biological weathering are outlined.

The effects of weathering on the nature of the landscape are evident in almost all landforms. On the surface of many landforms we can find layers of soil and regolith. Soil and regolith represent the accumulation of small particles of rocks and minerals that were derived from disintegration of much large pieces of bedrock. The region of the earth with the most active soil formation is the tropics because of high temperatures and an abundance of moisture. In regions of limestone bedrock, the effects of chemical solution can produce a number of unique geomorphic features that are the result of the dissolving and deposition of calcium carbonate. High latitude regions of the world also have landform features that are the result of weathering. Freeze-thaw action and frost-shattering along with the action of some other geomorphic processes cause the formation of a number of types of patterned ground.

In the previous lectures we learned that one of the by-products of rock weathering was the development of soils. However, soils are much more than just an assortment of fine mineral particles. A true soil is composed of 4 things: mineral particles, air, water, and organic material. A true soil is also the product of the activities of living organisms. There are also a number of features found in a true soil that distinguish it from simple mineral sediments. True soils are influence, modified, and supplemented by living organisms. Living organisms are the source of the organic matter found in soils. They also are responsible for decomposing organic matter into humus and then finally back into inorganic elements and compounds.

Soils often show the effects of translocation of clay and dissolved substances because of the downward movement of water through the soil profile. The process of removal of these materials from a horizon within the soil is called eluviation. The deposition of these material in a deeper layer is called illuviation. The complete removal of chemical substances from a soil is known as leaching.

The particles that make up a soil can be three size types: clay; silt; and sand. Some soils are composed of just one particle type. A loam is a soil that has equal quantity of clay, silt, and sand. Of these particles clay is probably the most important. Because of its large surface area, clay has the ability to hold onto large quantities of nutrients.

A variety of inorganic and organic chemical reactions occur within a soil horizon. One effect of these reactions is that soils can become acidic or alkaline in pH. Soil pH also influences the fertility of a soil. The most fertile soils have a pH that is around neutral.

Soil can vary in their color. Color can be used as a indicator of processes acting on a soil or the acumulation of organic matter and other substances.

The last distictive characteristics of a soil is the presence of horizontal layers or horizons. These layers are the result of a variety of processes. Up to five different primary layers can be found: 0 - organic layer; A - topmost mineral that is rich in organic matter and influence by eluviation; B - Illuviation layer; C - layer not pedogenically developed; and R - unweathered bedrock.

The process of soil development is called pedogenesis. Pedogenesis is the result of five factors: climate; living organisms; parent material; topography; and time. Climate influences soils by influencing rates of weathering, organic matter decomposition, and soil chemical reactions. Living organisms influence soil development through organic matter accumulation, profile mixing, and biogeochemical cycling. Parent material influences soil texture, soil chemistry, and nutrient cycling. Pedogenesis is influenced by topographyÕV,s effect on microclimate and drainage. Time influences the temporal consequences of all of the factors above.

At the macro-scale we can suggest that there are five main principal pedogenic processes. These processes are laterization, podzolization, calcification, salinization, and gleization.

Soil classification systems have been created to provide scientists and resource managers with a system to determine the charateristics of a soil in a particular location. Several different classification systems exist. We are interested in two systems. The United States Soil Classification System recogizes eleven distinct soil orders: oxisols, aridsols, mollisols, alfisols, ultisols, spodsols, entisols, inceptisols, vertisols, histosols, and andisols. The Canadian System of Soil Classification was designed to classify soils that develop in Canada's cool climatic environment. The Canadian System recognizes nine different orders: Brunisols, Chernozems, Cryosols, Gleysols, Luvisols, Organic, Podzols, Regosols, and Solonetzic.

Erosion is the removal and transport of material from the surface of the Earth. The energy from erosion comes from a variety of sources that generally act because of gravity. Erosion normally involves three processes: detachment, entrainment and transport. Detachment usually begins the process of erosion. Sometimes it can involve the breaking of bonds that hold particles together. Entrainment is the operation of lifting particles by and into the agent of erosion. Because most particles bond with other particles more erosive energy is require to lift a particle than to transport it. Transportation of particles can occur in four different ways: suspension, saltation, traction and solution. The exact mechanism, which moves a particle, is dependent on the weight, size, shape, and surface configuration of the grain of sediment and the viscosity of the erosive agent.

Deposition occurs when the erosive agent can no longer move, dissolve or suspend eroded particles. In most cases, deposition requires a reduction in the flow velocity of the erosive agent. It can also involve evaporation, as in the case of dissolved ions in water, or melting, as in the case of glacial erosion and transport. For most particles deposition is not a onetime event. Most particles under go repeated cycles of erosion and deposition before they come to their final rest.

Most of the terrestrial landscape consists of a mosaic of hillslope types. A number of geomorphic processes act on these landforms causing them to be worn and eroded over time. The erosion of hillslopes ends, or reaches equilibrium, when the sediments and rocks that make up hills are redistributed more evenly on the Earth's surface. Geomorphologists tend to view hillslope processes a series of system inputs and outputs. Inputs to the hillslope system include sediments from weathering, solar radiation, and water from precipitation. Outputs occur by way of evapotranspiration, percolation, groundwater flow, runoff, stream flow, and the flow of glacial ice. Some of the above processes also move sediment from hillslopes. The movement of sediments through the hillslope system without the help of the erosional mediums of wind, water and ice is know as mass wasting.

Mass wasting consists of a number of processes whose action causes the downslope movement of sediments. All of these processes are powered by gravity. The development of hillslope instability and mass wasting depends on a number of factors that influence the stress exerted on sediments. If these stresses greatly exceed the internal strength holding slope materials in place the slope failure tends to be large in size and rapid. Slow long-term failures develop when the stresses acting on the hillslope just exceed the internal strength of the slope materials. We can group the various types of mass wasting into three different groups based on the characteristic of the slope materials. In slopes formed from non-cohesive coarse-grained sediments mass wasting occurs by way of: the sliding and rolling of individual particles; through the chaotic avalanche or many particles; or by the process of shallow sliding of a large number of particles along a plane of weakness. Slopes formed on cohesive materials like clay and silt have different set of processes involved in their mass wasting. The main processes of mass wasting on cohesive sediments are rotational slips, mudflows and soil creep. A number of hillslopes are composed of large masses of rock. Rock normally has strong internal granular bonds allowing slopes made of this material to maintain steep grades. Mass wasting on hard rock slopes generally occurs along bedding planes and joints found in the rock.

Streams modify the landscape through the movement of water and sediment. Streams are very powerful erosive agents especially during periods of flooding. The sediments removed by streams are usually deposited downstream in floodplains, lakes, and ocean basins. Streams and their floodplains vary in their characteristics along the typical long profile of a stream. The grade of the long profile represents a balance between erosion and deposition processes. At the headwaters streams flow quickly (because of a steep grade) in narrow v-shaped valleys. Depositional features are rare. Further down the profile a profound change occurs in the stream gradient. This change reduces velocity causing the stream to drop its coarser sediments in a floodplain. The channels of these streams is braided. The gradient of the stream becomes very shallow in the last part of the long profile. Now the stream channel takes on meandering and floodplain deposits are spread over a larrge area.

The amount water flowing through a stream channel is commonly referred to as stream discharge. Discharge quantity is controlled water velocity, width of the channel, and the depth of the channel. These variable also change with velocity increases or decreases over time. Flow within the stream channel is allways at a maximum at the center of the stream. The channel bottom and banks reduce flow velocity because of friction. In three-dimensions, the zone of maximum flow or thalweg moves from side to side and up and down. A closer examination of flow indicates that three types of flow occur: laminar flow; turbulent flow; and helical flow.

All streams carry sediment. The actual amount is related to the characteristics of the materials on which the stream flows. Usually, an increase in discharge results in an increase in the amount of sediment that is carried.A sediment rating curve models the relationship between discharge and the amount of sediment carried. Now within the stream sediment can be carried in three ways: bed load; suspended load; and dissolved load.

One of the most obvious landforms created by streams are the channels they flow in. We can classify stream channels into three types. Channels located in the upper reach of streams are V-shaped, narrow, and deep with little associated floodplain. These channels are often cut into bedrock and limited bed sediments consist loose rocks and boulders. Stream channels become shallow, wide, and braided when the stream gradient changes from being steep to gently sloping. Shallow braided channels are created by the presence of sand and gravel beds in a floodplain. These sediments are deposited because a sudden change in gradients causes a reduction in flow velocity. Often a drastic change in grade also causes the deposition of an alluvial fan. Channels become U-shaped and meandering with continued reduction in stream gradient. Meandering channels flow over an extensive floodplain of complex deposits.

We can describe a number of features within the stream channel. Streams carrying coarse loads develop sand and gravel beds when velocity is reduced spatially or temporally. Point bars are common in meandering streams devloping on the inside of channel bends. In straight streams, bar deposits form in relation to the thalweg. Some other features associated with the thalweg include riffles and pools. Some other features common within the stream channel are dunes and ripples. These features form on the channel bottom when the bed is composed of sand and silt.

Floodplains are flat areas adjacent to stream channel that are composed primarily of deposits put down during episodes of floods. A number of features are found on the floodplain. Some of these features are depositional like levees, abandoned point bars, and depressions. Other features like crevasses and Oxbow lakes are created by erosion.

When a stream ends its flow into a lake or ocean the sediment it carries will be deposited to create a delta. Deltas are complex features made up of 3 different bed types. Deltas also have a variety of different shapes.

Scientists often view streams as being part of a drainage basins. Drainage basins are arbitrarily defined by topography. Drainage basins are a very useful geomorphic concept and they are oftem modeled as open systems. Within a drainage basin inputs and factors like topography, soil type, bedrock type, climate, and vegetation influence a number of stream properties. One stream property that is effected by these factors is the drainage pattern of streams.

Stream morphometry is all about exploring the mathematical relationships between various stream attributes. Studies have discovered that these relationships can be view as laws because of their geometric or mathematical predictability. These measurements can also be used to compare streams and basins to identify factors that may be causing differences.

Landforms of coastal regions are in most cases shaped by the geomorphic action of ocean waves. Ocean was can exert a significant amount of energy through the kinetic energy of wave motion. The energy of ocean waves on the terrestrial landscape of the Earth is concentrated at the shoreline. At the shoreline the energy wave motion causes erosion and the transport of sediment. Erosion along the shoreline is normally greatest at areas where wave refraction causes the intensification of wave energy. Deposition occurs along the shoreline when wave energy is reduced in it intensity and when sediment is transported into an area by beach drift and longshore drift

During the last billion years of Earth history there have been several periods where global average temperatures were much colder than they are today. The colder climates lead to the formation an expansion of extensive continental and alpine glaciers. The last period of glacial advance began about 2 million years ago. For the past 14,000 years we have been experiencing a warming of the global climate which has lead to a retreat of glaciers. Today glaciers cover about 10 % of the Earth's land surface. During the height of the last glacial advance about 30% of the Earth's land surface was covered. Geomorphologists have classified glaciers based on size.

The growth of glaciers first involves the conversion of snow into glacial ice. This process takes many years and the weight of overlying deposits to covert snow with a density between 50 to 300 kilograms per cubic meter to ice with a density of 850 kilograms per cubic meter. For mass of ice to be classified as a glacier it most have the ablity to move. This occurs when the mass of ice becomes so heavy that it begins to flow by plastic deformation. Masses of ice in mountain valleys begin to flow when accumulations become more than 20 meters high. Rates of flows within glaciers is influenced by factors like friction, ice weight, and slope of the valley. Some glaciers are able to move more quickly because they experience basal sliding.

Scientists oftem view glaciers as systems that are influenced by a number of inputs and outputs. Some of these inputs and outputs influence the glaciers ability to surge or retreat. The concept of glacier mass balance suggests that a glacier is influenced by two processes: accumulation and ablation. If accumulation exceeds ablation the glacier surges forward. If ablation exceeds accumulation the glacier surges retreats.

Glaciers have played an important role in shaping the landscape of the middle and higher latitudes. The effects of glaciers exist at essentially two scales. Alpine glaciers modify landcapes on a local scale. Many alpine glaciers are still operating today in the world's mountainous regions. Continental glaciers influenced landscapes on the regional and continental scale. Most of these glaciers are now gone, but the evidence of their action is still quite obvious.

Glacial landforms that are the result of erosion can once again occur at two scales. On the local scale, alpine glaciers are responsible for the following erosional features: U-shaped valleys, hanging valleys, cirques, horns, and aretes. Continential glaciers removed large amount of surface sedments on the areas that they occurred. Sometimes this removal of material left large depression which are now filled with lakes of all sizes. Both types of glaciers leave the following depositional features: till, moraines, outwash plains, and erratics. The size of these deposits is of course much large for the continental glaciers. Continental glaciers also produce a number unique deposits like: kame, eskers, and drumlins.

About 25% of the Earth's terrestial surface is influenced by periglacial processes. The most important process of periglacial environments is freeze-thaw action. Extreme cold temperatures of periglcial environments often causes surface soils and sediments to freeze. These frozen sediments are called permafrost. Many types of permafrost have been classified. Permafrost can have a depth of up to 1500 meters. On its surface, is a layer that is subject to seasonal thawing. This layer is called the active layer. Sheets of permafrost can have unfrozen layers on top, beneath, or within it. These unfrozen layers are called taliks.

Periglacial areas are also known for the presence of ground ice. Ground ice comes in a variety of differnt forms and each type has unique characteristics and processes of formation. A number of geomorphic processes operate in periglacial regions. One process that is quite active in periglacial regions is physical weathering due to the crystallization of water. This process can create vast quantities of shattered angular rock on the periglacial landscape. Mass movement is common in periglacial regions of the world. The main processes that resulting mass movement include solifluction, gelifluction, frost creep, and rockfalls. Finally, erosion occurs in periglacial environment by way of nivation, eolian processes, and fluvial processes.

Three types of landforms are common in periglacial environments. The first is patterned ground. Pattern gound comes in a variety of shapes including stripes, steps, circles, polygons, and nets. A number of processes are involved in the formation of these similar features. Periglacial environments are also characterized by the presence of ice mounds. Palsas are low elongated mounds with cores of segregated ice and peat. The other type of ice cored hill is called a pingo. These features are much larger than palsas and are formed by either cryostatic pressure or artesian groundwater flow.

Places in the arid regions and coastal areas of the world are influence by wind. The speed of these winds is great enough to move soil particles that range in size from clay to sand. Material is transport by wind by three processes: traction, saltation, and suspension. The power of wind produces a variety of eolian erosional features. Some of these features include deflation hollows, pans, and desert pavement. Wind also produces a variety of deposional features. Sand dune are the most noticable feature of deposition. Sand dunes come in a variety of forms that are produced by a range of processes.Another important deposit of eolian forces is loess. Many deposits of loess were formed in the past when winds blew over glacial deposits during the pleistocene.


List of Key Terms

Ablation, Abrasion, Abyssal Fan, Accretion, Accumulation, Acidic, Acidic Solution, Active Layer, Aftershock, Aggradation, A Horizon, Alkaline, Allophane, Alluvial Fan, Alluvium, Alpine Glacier, Alpine Permafrost, Amphibole, Andesite, Anticline, Arêtes, Arkose, Artesian, Asthenosphere, Atmosphere, Atom,

Backwash, Bacteria, Bank-Caving, Bar, Barrier Beach, Basal Sliding, Basalt, Basalt Plateau, Basaltic Magma, Basement Rock, Basic, Batholith, Bay, Bayhead Beach, Bay-Mouth Bar, Beach, Beach Drift, Bed, Bed Load, B Horizon, Bifurcation Ratio, Biogeochemical Cycling, Biological Weathering, Biosphere, Biotite, Blowout, Body Wave, Bottomset Bed, Boulder, Bowen Reaction Series, Braided Stream, Breaker, Breccia,

Calcification, Calcium Carbonate, Caldera, Caldera Volcano, Caliche, Calving, Canadian Shield, Canyon, Carbonation, Cation, Cave, Cavitation, Cenozoic, Chalk, Chelate, Chelation, Chemical Weathering, C Horizon, Cinder Cone, Cirque, Cirque Glacier, Clastic, Clay, Cleavage, Closed Talik, Coal, Cold Glacier, Composite Volcano, Compound, Conduction, Conglomerate, Coniferous Vegetation, Contact Metamorphism, Continental Crust, Continental Drift, Continental Glacier, Continental Margin, Continental Plate, Continental Rise, Continental Shelf, Continental Shelf Break, Continental Slope, Continuous Permafrost, Convection, Core, Craton, Creep, Cretaceous, Crevasse, Critical Entrainment Velocity, Crust, Cryostatic Pressure, Cuspate Foreland,

Debris Flow, Decomposition, Deflation Hollow, Delta, Density, Deposition, Depositional Landform, Depression, Desert Pavement, Detachment, Diorite, Dip, Discontinuous Permafrost, Dissolved Load, Disturbance, Dolomite, Drainage Basin, Drainage Density, Drumlin, Dune, Dune Field, Dyke, Dynamic Metamorphism,

Earthquake, Earthquake Focus, Ecosystem, Eddy, Element, Eluviation, Energy, Entrainment, Eon, Epicenter, Epoch, Equilibrium, Era, Erosion, Erosional Landform, Erratics, Esker, Eukaryotic, Evaporation, Evapotranspiration, Evaporite, Evolution, Extrusive Igneous Rock,

Fault, Faulting, Feldspar, Felsic Magma, Ferricrete, Fetch, Firn, Firn Limit, Fissure, Flocculation, Flood, Floodplain, Fluid Drag, Fold, Folding, Foliation, Food Chain, Foreset Bed, Forminifera, Freeze-Thaw Action, Friction, Frost Creep, Frost Wedging,

Gabbro, Gelifluction, Glacial, Geologic Time Scale, Glacial Drift, Glacial Milk, Glacial Polish, Glacial Retreat, Glacial Surge, Glacier, Glaciofluvial, Gneiss, Graben Fault, Granite, Granitic Magma, Granitic Pluton, Grasslands, Gravel, Gravity, Ground Ice, Groundwater, Groundwater Flow, Gypsum,

Halite, Hanging Valley, Headland, Headwaters, Helical Flow, Holocene Epoch, Horn, Horst Fault, Humus, Hydration, Hydrocarbon, Hydrolysis, Hydrosphere,

Ice, Ice Age, Ice Lense, Ice Wedge, Igneous Intrusion, Igneous Rock, Illuviation, Infiltration, Inner Core, Inorganic, Insolation Weathering, Interglacial, Intrusive Igneous Rock, Ion, Island Arc, Isostacy, Isostatic Rebound,


Kame, Karst, Kettle Hole, Kinetic Energy,

Landslide, Laurasia, Lava Flow, Lignite, Limestone, Lithification, Lithosphere, Lithospheric Hot Spot, Logarithmic Scale, Lower Mantle,

Lake, Laminar Flow, Lateral Moraine, Laterite, Law of Basin Areas, Law of Stream Lengths, Law of Stream Numbers, Leaching, Lee-Side, Leeward, Levee, Limestone, Lithification, Lithosphere, Litter, Litterfall, Little Ice Age, Littoral Drift, Lobe, Loess, Longshore Current, Longshore Drift,

Mafic Magma, Magma, Magma Plume, Magnitude, Mantle, Marble, Mass Wasting, Metamorphic Rock, Metamorphism, Metasomatic Metamorphism, Mica, Mid-Oceanic Ridge, Mineral, Monocline, Mudstone, Muscovite,

Magma, Mass, Mass Balance, Mass Movement, Mass Wasting, Meander, Medial Moraine, Melting, Meltwater, Metamorphism, Mid-Latitude Cyclone, Mineral, Moraine, Mountain Glacier, Mouth, Morphometry, Mudflow,

Needle Ice, Negative Feedback, Névé, Nivation, Nivation Hollow, Non-Clastic,

Obsidian, Ocean Basin, Oceanic Crust, Ocean Floor, Oceanic Plate, Oceanic Trench, Olivine, Organic Matter, Orogeny, Outer Core, Overthrust Fold,

Ocean, Ocean Basin, O Horizon, Open Talik, Organic Matter, Outwash, Outwash Plain, Oxidation, Overbank Flow, Oxbow Lake,

Paleoclimatic, Pangaea, Peridotite, Period, Permian, pH, Phanerozoic, Plagioclase Feldspar, Plate Tectonics, Platform, Pleistocene, Pluton, Plutonic Igneous Rock, Polycyclic Landform, Polygenetic Landform, Potential Energy, Precambrian, Precipitation, Process-Response System, Prokaryotic, Pyroxene, P-wave,

Paleoclimatic, Palsa, Pan, Patterned Ground, Peat, Pebble, Pedogenesis, Percolation, Periglacial, Permafrost, pH, Physical Weathering, Piedmont Glacier, Pingo, Plate Tectonics, Pleistocene, Plucking, Podzolization, Point Bar, Pools, Pore Ice, Positive Feedback, Potential Energy, Precipitation, Pressure Melting, Process-Response System, Profile,

Quartz, Quartzite, Quaternary,

Recumbent Fold, Regional Metamorphism, Reverse Fault, Rhyolite, Richter Scale, Rift Valley, Rift Zone, Rock, Rock Cycle, Runoff,

Rain, Raindrop Impact, Rainsplash, Rainwash, Recessional Moraine, Reduction, Reg, Regolith, R Horizon, Riffles, Rill, Rip Current, Ripples, Roche Moutonnee, Rock, Rockfall, Rock Slide, Rotational Slip, Runoff,

Sand, Sandstone, Schist, Sea-Floor Spreading, Sea-Level, Sedimentary Rock, Seismic, Seismic Wave, Seismograph, Shale, Shield, Shield Volcano, Silica, Silicate Magma, Silcrete, Sill, Silt, Siltstone, Slate, Stream Flow, Strike-Slip Fault, Structural Landform, Subduction, Subduction Zone, Submarine Canyon, Subsidence, Surface Wave, Syncline, S-wave, Salinization, Saltation, Sand, Sand Dune, Sand Sheet, Sand Wedge, Scree, Sea Arch, Sea Cliff, Sea Stack, Sediment, Sedimentary Rock, Sediment Rating Curve, Seepage, Segregated Ice, Seismic Wave, Shale, Sheetwash, Shore, Shoreline, Silicate, Silt, Slaking, Snout, Snow, Snow Line, Snow Melt, Soil, Soil Creep, Soil Profile, Soil Texture, Solar Radiation, Solifluction, Solution, Specific Heat, Spit, Sporadic Permafrost, Spring, Steady State, Stoss-Side, Stream, Steam Bank, Stream Bed, Stream Channel, Stream Discharge, Stream Load, Stream Long Profile, Striations, Sublimation, Subsea Permafrost, Suspended Load, Suspension, Swash, Swell, System,

Tectonic Plate, Tephra, Tertiary, Tetrahedron, Thermal Metamorphism, Transform Fault, Tsunami,

Talik, Talus, Talus Cone, Temperate Glacier, Terminal Moraine, Terminal Fall Velocity, Terminal Velocity, Terminus, Thalweg, Threshold Velocity, Throughflow, Through Talik, Thunderstorms, Tidal Current, Till, Till Plain, Tombolo, Topset Bed, Traction, Transport, Turbulent Flow,

Unloading, Ultramafic, Uniformitarianism, Upper Mantle,

Velocity, Volcanic Ash, Volcanic Igneous Rock, Volcanic Pipe, Volcano, Vortice,

Watershed, Water Table, Wave, Wave Crest, Wave-Cut Notch, Wave Height, Wavelength, Wave Period, Wave Refraction, Wave Trough, Weathering, Weathering Landform, Wetting and Drying, Wind Ripple, Windward,

Zone of Ablation, Zone of Accumulation,


Study Questions, Problems, and Exercises

Essay Questions

(1). Discuss in detail the formation of sedimentary rocks. Also, include in your answer information concerning their composition, lithification, and naming.

(2). Explain why the theory of plate tectonics explains lithospheric phenomena like earthquakes, mountains, volcanoes, folding, and faulting.

(3). Compare and contrast the structure, composition, and formation of igneous and sedimentary rocks.

(4). Discuss the classification of clastic sedimentary rocks according to particle types.

(5). Outline the Bowen reaction series. What does it tell us about the formation of minerals in igneous rocks?

(6). What geologic features are found at the boundaries of tectonic plates? Briefly explain how plate tectonics is responsible for their formation or occurrence.

(7). What evidence exists for the theory of plate tectonics

(8). Describe the various types of igneous rocks that exist according crystal size, magma chemistry, and the quantity of various mineral types.

(9). Discuss how heat, pressure, and the chemical action of fluids act to create metamorphic rocks. Describe some of the common types of metamorphic rocks.

(10). What is the difference between clastic and non-clastic sedimentary rocks? What are the two general types of non-clastic sedimentary rocks that exist? Finally, give two examples of each of these three rock types.

(11). What are the eight most common elements found in minerals? Describe the nine major groups of minerals.

(12). Describe the various layers that make up the solid Earth.

(13). Describe the various physiological features associated with the ocean basins.

(14). What is a volcano? Where and why do they form? Describe the five different types of volcanoes.

(15). Describe the various physiological features associated with the Earth's terrestial surface.

(16). Describe the various physiological features associated with the Earth's ocean basins.

(17). Outline the various processes of physical, chemical, or biological weathering.

(18). Erosion can be seen as three processes: detachment, entrainment and transport. Discuss these three processes in relation to following two erosional mediums: water and ice.

(19). Discuss the nature of hillslope failure processes as related to cohesive and non-cohesive materials slope materials.

(20). Describe the physical characteristics of a location that would favor each of the following types of mass movements: rockfall, rockslide, mudflow, slump, and creep.

(21). What is a glacier? What conditions are necessary for a glacier to form? Why did continental glaciers form over certain specific regions of the North American continent?

(22). Describe the overall impact of extensive alpine glaciation on the mountainous regions of British Columbia. What are some of the more important erosional and depositional landforms?

(23). By what processes do waves and currents erode coasts? Briefly describe each process?

(24). What coastal environmental conditions favor coastal erosion? What conditions favor coastal deposition?

(25). How do glaciers influence the surface configuration of the Earth by way of erosion and deposition? Give plenty of examples in your answer.

(26). What are some of the common features associated with continental glaciation? How are these features formed?

(27). Briefly describe SIX depositional features associated with continental glaciation.

(28). How does beach drift and longshore drift move sediment along coastlines?

(29). What factors often trigger mass movement?

(30). Describe the various processes that operate in periglacial regions.

(31). Describe the common landforms found in periglacial regions.

(32). Describe some of the landforms common to environments influenced by eolian processes.

(33). Describe some the important characteristics of soil.

(34). What five factors are important in pedogenesis? Explain. Outline how the pedogenic processes operate.

(35). Describe the Canadian and US systems of soil classification.







Created by Dr. Michael Pidwirny & Scott Jones University of British Columbia Okanagan

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Copyright © 1999-2009 Michael Pidwirny

05/25/2009 9:52