physical geology
examines the materials composing Earth and the processes that operate beneath and upon its surface.
Historical geology
seeks to understand the origin of Earth and its development through time.
Catastrophism
states that earth's landscapes developed over short time spans primarily as a result of great catastrophes
Uniformitarianism
one of the fundamental principles of modern geology advanced by James Hutton in the late 1700s, states that the physical, chemical, and biological laws that operate today have also operated in the geologic past. The idea is often summarized as "The presen
By applying such principles as the law of superposition and the principle of fossil succession.
How do scientists develop a geologic time scale?
The solid Earth (or geosphere), the water portion of our planet (the hydrosphere), and Earth's gaseous envelope (the atmosphere). Also the biosphere (life)/
Three major parts of Earth's physical environment?
A system
A group of interacting parts that form a complex whole
Closed system
energy moves freely in and out, but matter does not enter or leave the system.
Positive feedback mechanisms
natural systems that tend to enhance change
negative feedback mechanism
natural systems that tend to resist change and thus stabilize the system.
1) The Sun, which drives the external processes that occur in the atmosphere, hydrosphere, and at Earth's surface, and
(2) Heat from Earth's interior that powers the internal process�es that produce volcanoes, earthquakes, and mountains.
Two sources of energy that power the Earth system?
Rock Cycle
one of the many cycles or loops of the Earth system in which matter is recycled. It illustrates the origin of the three basic rock groups and the role of various geologic processes in transforming one rock type into another.
Nebular hypothesis
Describes the formation of the solar system. The planets and Sun began forming about 5 billion years ago from a large cloud of dust and gases. As the cloud contracted, it began to rotate and assume a disk shape. Ma�terial that was gravitationally pulled t
based on differences in chemical composition and on the basis of changes in physical properties
How are Earth's internal structures divided?
Lithosphere, asthenosphere, mesophere, outer core, inner core.
What are the layers inside the Earth?
Lithosphere
the cool, rigid outermost layer that averages about 100 kilometers think.
Asthenosphere
the solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it
Mesosphere
Where rocks are very hot and capable of very gradual flow
outer core
a layer of molten iron and nickel that surrounds the inner core of Earth where Earth's magnetic field is generated
Inner core
a dense sphere of solid iron and nickel at the center of Earth
continents and ocean basins. The elevation differences between continents and ocean basins are primarily the result of differences in their respective densities and thicknesses.
Two different divisions of Earth's surface and a significant difference
mountain belts and the stable interior
The largest features of hte continents can be divided into two categories?
continental margins, deep-ocean basins, and oceanic ridges.
ocean floor is divided into three major topographic units.
Plate tectonics theory
provides a comprehensive model of Earth's internal workings. It holds that Earth's rigid outer lithosphere consists of several segments called plates that are slowly and continually in motion relative to one anoth�er. Most earthquakes, volcanic activity,
(1) divergent boundaries, where plates move apart; (2) convergent bound-aries, where plates move together, causing one to go beneath another, or where plates collide, which occurs when the lead�ing edges.<are made of continental crust; and (3) transform f
Three distinct types of plate boundaries?
Mineral
naturally occurring inorganic solid possessing a definite chemical structure that gives it a unique set of physical properties. Most rocks are aggregates composed of two or more.
elements.An element is a large collection of electrically neutral atoms, all having the same atomic number.
building blocks of minerals?
compounds
Atoms combine with each other to form more complex sub�stances called..?
Isotopes
variants of the same element. Some are unstable and disintegrate naturally through a process called radioactivity. Also, it's atoms of the same element that have different numbers of neutrons
crystal form, luster, color, streak, hardness, cleavage, fracture, and density or specific grav�ity. In addition, a number of special physical and chemical properties (taste, smell, elasticity, malleability, feel, magnetism, double refraction, and chemica
Properties of minerals
oxygen, sili�con, aluminum, iron, calcium, sodium, potassium, and magnesium
Of the nearly 4000 minerals, no more than a few dozen make up most of the rocks of Earth's crust and, as such, are clas�sified as rock-forming minerals. 8 elements make up the bulk of these minerals and repre�sent over 98 percent (by weight) of Earth's co
Silicates. All silicate minerals have the negatively charged silicon-oxygen tetra�hedron as their fundamental building block. Each silicate mineral has a structure and a chemical composition that indicates the con�ditions under which it was formed.
most common mineral group.
carbonate minerals, calcite and dolomite. Two other nonsilicate minerals frequently found in sedimentary rocks are halite and gypsum.
The nonsilicate mineral groups contain several eco�nomically important minerals. The more common nonsilicate rock-forming miner�als include the...
reserves/deposits
Mineral resources are the endowment of useful minerals ul�timately available commercially. Resources include already identified deposits from which minerals can be extracted profitably, called _____, as well as known ____ that are not yet economically or
when magma cools and solidifies. Extrusive, or volcanic, igneous rocks result when lava cools at the surface. Magma that solidifies at depth produces in-trusive, or plutonic, igneous rocks
When do igneous rocks form?
Crystallization
As magma cools, the ions that compose it arrange them�selves into orderly patterns during a process called
Slow cooling results in the formation of rather large crystals. Conversely, when cooling occurs rapidly, the outcome is a solid mass consisting of tiny intergrown crys�tals. When molten material is quenched instantly, a mass of unordered atoms, referred t
How does the rate of cooling affect size of crystals?
Texture and mineral composition
How are Igneous rocks classified?
The texture of an igneous rock refers to the overall appear�ance of the rock based on the size and arrangement of its in�terlocking crystals. The most important factor affecting texture is the rate at which magma cools. Common igneous rock textures includ
texture of an igneous rock? what it refers to, what affects it, and common ones?
The mineral composition of an igneous rock is the conse�quence of the chemical makeup of the parent magma and the environment of crystallization. Igneous rocks are di�vided into broad compositional groups based on the per�centage of dark and light colored
Mineral composition of an igneous rock
the chemical composition of the magma from which it crystallizes. As magma cools those minerals with higher melting points crystallize before minerals with lower melting points.
The mineral makeup of an igneous rock is ultimately de�termined by?
crystal setting
During the crystallization of magma, if the earlier-formed minerals are denser than the liquid portion, they will settle to the bottom of the magma chamber during a process called ?
magmatic differentiation
Owing to the fact that crystal settling removes the earlier-formed minerals; the remaining melt will form a rock with a chemical composition much differ�ent from the parent magma. The process of developing more than one magma type from a common magma is c
assimilation or magma mixing
Once a magma body forms, its composition can change through the incorporation of foreign material, a process termed?
Magma originates from essentially solid rock of the asthenosphere. In addition to a rock's composition, its tem�perature, depth (confining pressure), and water content de�termine whether it exists as a solid or liquid.
what determines whether magma exists as a solid or liquid?
partial melting
Because melting is generally not complete, a process called ____ produces a melt made of the lowest-melting-temperature minerals, which are higher in silica than the original rock. Thus, magmas generated by partial melting are nearer to the felsic (granit
igneous processes.
Some of the most important accumulations of metals, such as gold, silver, lead, and copper, are produced by what?
The best-known and most important ore deposits are generated from hydrothermal (hot-water) solutions. Hydrothermal deposits are thought to or
the magma's composition, its temperature, and the amount of dissolved gases it contains. As lava cools, it begins to congeal, and as viscosity increases, its mobili�ty decreases. The viscosity of magma is directly related to its silica content. Rhyolitic
The primary factors that determine the nature of volcanic eruptions
(1) lava flows (pahoehoe flows, which resemble twisted braids; and aa flows, consisting of rough, jagged blocks; both form from basaltic lavas); (2) gases (primarily water vapor); and (3) pyroclastic material (pulverized rock and lava fragments blown from
Materials associated with a volcanic eruption
Shield cones
are broad, slightly domed volcanoes built primarily of fluid, basaltic lava
Cinder cones
volcano. have steep slopes composed of pyroclastic ma�terial
Composite cones
or stratovolcanoes, are large, nearly symmetrical structures built of interbedded lavas and py�roclastic deposits. _______cones produce some of the most violent volcanic activity. Often associated with a vio�lent eruption is a nuee ardente, a fiery cloud
calderas
Most volcanoes are fed by conduits or pipes. As erosion pro�gresses, the rock occupying the pipe is often more resistant and may remain standing above the surrounding terrain as a volcanic neck. The summits of some volcanoes have large, nearly circular de
Fissures
Although volcanic eruptions from a central vent are the most familiar, by far the largest amounts of vol�canic material are extruded from cracks in the crust called
Flood basalt
describes the fluid, water-like, basaltic lava flows that cover an extensive region in the northwestern United States known as the Columbia Plateau. When silica-rich magma is extruded, pyroclastic flows consisting largely of ash and pumice fragments usu�a
according to their shape and by their orientation with respect to the host rock, gen�erally sedimentary rock/\.The two general shapes are tabular (sheetlike) and massive. Intrusive igneous bodies that cut across existing sedimentary beds are said to be di
Intrusive igneous bodies are classified by?
Dikes
are tabular, discordant igneous bodies produced when magma is injected into fractures that cut across rock layers.
sills
Tabular, concordant bodies, form when magma is injected along the bedding surfaces of sedimentary rocks. In many respects, ___ closely resemble buried lava flows.
Laccoliths
are similar to sills but form from less fluid mag�mas that collect as lens-shaped masses that arch the over�lying strata upward
Batholiths
the largest intrusive igneous bodies, frequently
make up the cores of mountains, as ex�emplified by the Sierra Nevada.
divergent plate boundaries
Ac�tive areas of volcanism are found, along oceanic ridges where seafloor spreading is occurring
convergent plate boundaries
in the vicinity of ocean trenches where one plate is being subducted beneath another
intraplate volcanism
in the interiors of plates themselvesRising plumes of hot mantle rock are the source of most ___ volcanism
Weathering
the disintegration and decomposition of rock at or near the Earth's surface
Mass Wasting
the transfer of rock material downslope by gravity.
Erosion
the removal of material by wind, water, or ice.
Mechanical weathering
the physical breakup of rock by frost wedging, salt crystal growth, unloading and biologic activity.
Chemical weathering
alters the composition of rock. Water containing oxygen and (or) carbon dioxide is the most important agent.
particle size, mineral makeup, and climatic factors, particularly temperature and moisture
Rates of weathering depends on?
Rcomposition and amount of exposed surface area.
Rocks weather at different rates depending on?
soil
the portion of regolith (rock and mineral fragments) that is a combination of mineral and organic matter, water, and air.
soil characteristics, climate, slope and plant cover.
Weathering creates particles capable of being eroded, transported and eventually deposited. Rates of erosion are influenced by?
Weathering may create ore deposits by concentrating minor amounts of metals into economically valuable deposits. Processes include removing nonvaluable components of the rock or, in contrast, removal and later concentration of the valuable components.
How can weathering create ore?
(1) as detrital material, which originates and is transported as solid particles from both mechanical and chemical weathering, which, when lithified, forms detrital sedimentary rocks; and (2) from soluble material produced largely by chemical weathering,
Two basic principles of sedimentary rock
The size of the particles in a detrital rock indicates the energy of the medium that transported them. For example, gravels are moved by swift�ly flowing rivers, whereas less energy is required to trans�port sand. Common detrital sedimentary rocks include
how do you distinguish among various detrital sedimentary rocks?
1) by inorganic processes, such as evaporation and chemical ac�tivity; or (2) by organic processes of water-dwelling organ�isms that produce sediments of biochemical origin. Limestone, the most abundant chemical sedimentary rock, consists of the mineral c
Precipitation of chemical sediments occurs in two ways:
Diagenesis
refers to all of the physical, chemical, and bio�logical changes that occur after sediments are deposited and during and after the time they are turned into sedi�mentary rock. Burial promotes ___. ____ in�cludes lithification.
Lithification
refers to the processes by which unconsolidated sediments are transformed into solid sedimentary rock. Most sedimentary rocks are ____ by means of compaction and/or cementation.
Compaction
occurs when the weight of overlying materials compresses the deeper sediments.
Cementation
the most important process by which sedi�ments are converted to sedimentary rock, occurs when sol�uble cementing materials, such as calcite, silica, and iron oxide, are precipitated onto sediment grains, fill open spaces, and join the particles.
Detrital and chemical
Two groups of Sedimentary rock
Detrital
All ___ rocks have a clastic texture, which consists of discrete fragments and particles that are cemented and compacted together. The main criterion for subdividing the ___ rocks is particle size. Common ____ rocks include conglomerate, sandstone, and sh
Chemical
The primary basis for distinguishing among different rocks in the ____ group is their mineral composition. Some ____ rocks, such as those deposited when seawater evaporates, have a nonclastic texture in which the minerals form a pattern of interlocking cr
Sedimentary environments
places where sediment accumulates. They are grouped into continental, marine, and transitional (shoreline) environments. Each is charac�terized by certain physical, chemical, and biological con�ditions. Because sediment contains clues about the environmen
Layers, called strata, or beds, are probably the single most characteristic feature of sedimentary rocks. Other features found in some sedimentary rocks, such as ripple marks, mud cracks, cross-bedding, graded bedding, and fossils, also give clues to past
Features of sedimentary rocks
nonmetallic resources
Earth materials that are not used as fuels or processed for the metals they contain are referred to as ___. Many are sediments or sedimentary rocks. The two broad groups of _____ are building materials and industrial minerals. Limestone, perhaps the most
sedimentary. Coal originates from large quantities of plant remains that accu�mulate in an oxygen-deficient environment, such as a swamp. More than 70 percent of present-day coal usage is for the generation of electricity. Air pollution from the sulfur-ox
coal, petroleum, and natural gas, the fossil fuels of our modern economy, are all associated with what type of rock?
Metamorphic
is the transformation of one rock type into another. ____ form from preexisting rocks (igneous, sedimentary, or other metamorphic rocks) that have been altered by the agents of ____, which include heat, pressure (stress), and chemically active fluids. Dur
The mineral makeup of the parent rock determines, to a large extent, the degree to which each metamorphic agent will cause change. Heat is the most important agent be�cause it provides the energy to drive chemical reactions that result in the recrystalliz
What causes metamorphic rocks?
foliation
develops as platy or elongated minerals are rotated into parallel alignment, recrystallize to form new grains that exhibit a preferred orientation, or are plas�tically deformed into flattened grains that exhibit a pla�nar alignment.
Rock cleavage
is a type of foliation in which .rocks split cleanly into thin slabs along surfaces where 'platy minerals are aligned
Schistosity
a type of foliation defined by the parallel alignment of medium- to coarse-grained platy minerals
Geneiss
Metamorphic rocks with a band�ed texture are called?
slate, phyllite, schists, and gneiss
Common foliated metamorphic rocks include
marble (parent rock: lime�stone) and quartzite (most often formed from quartz sand�stone).
Nonfoliated rocks include
(1) contact or thermal metamorphism, (2) hydrothermal metamorphism and (3) burial and subduction zone metamorphism, and (4) regional metamorphism. Contact metamorphism occurs when rocks are in contact with an igneous body, resulting in the formation of zo
The four geologic environments in which metamorphism commonly occurs are
hydrothermal metamorphism
occurs where hot, ion-rich fluids circulate through rock and cause chemical alteration of the constituent minerals. Most ____ alteration occurs along the oceanic ridge system where sea-water migrates through hot oceanic crust and chemically alters newly f
Regional metamorphism
takes place at con�siderable depths over an extensive area and is associated with the process of mountain building. A gradation in the degree of change usually exists in association with ____ metamorphism, in which the intensity of metamorphism (low- to h