GEOLOGY M2 Flashcards Combined

Petrology

the branch of geology that deals with rocks, including their origin, structure, changes, etc.

Applications of Petrology

The fields of engineering, environmental, and urban geology are broadly concerned with applying the findings of geologic studies to construction engineering and problems of land use.

The location of a bridge, for example, involves geologic considerations in selecting sites for the supporting piers. The strength of geologic materials such as rock or compacted clay that occur at the sites of the piers should be adequate to support the load placed on them.

Engineering geology

is concerned with the engineering properties of geologic materials, including their strength, permeability, and compactability, and with the influence of these properties on the selection of locations for buildings, roads and railroads, bridges, dams, and other major civil features.

Urban geology

involves the application of engineering geology and other fields of geology to environmental problems in urban areas.

Environmental geology

is generally concerned with those aspects of geology that touch on the human environment.

Environmental and urban geology

deal in large measure with those aspects of geology that directly influence land use.

Environmental and urban geology

These include the stability of sites for buildings and other civil features, sources of water supply (hydrogeology), contamination of waters by sewage and chemical pollutants, selection of sites for burial of refuse so as to minimize pollution by seepage, and locating the source of geologic building materials, including sand, gravel, and crushed rock.

Since the late 1990s the importance of environmental geology has increased considerably in most developed countries as societies become aware of the environmental impact of humankind.

Metamorphic

Igneous

Sedimentary

3 Subdivision of Petrology

Igneous Petrology

concerned with the identification, classification, origin, evolution, and processes of formation and crystallization of the igneous rocks.

Andesite

is a fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene, and biotite. The specimen shown is about two inches (five centimeters) across.

Igneous Petrology

Most of the rocks available for study come from the Earth's crust, but a few, such as eclogites, derive from the mantle.

The scope of igneous petrology is very large because igneous rocks make up the bulk of the continental and oceanic crusts and of the mountain belts of the world, and they also include the high-level volcanic extrusive rocks and the plutonic rocks that formed deep within the crust.

Some of the major problems within the scope of igneous petrology are:

form and structure of igneous bodies

crystallization history of the minerals

classification of rocks

fractionation of parent magmas

mechanism of generation of magmas

history of formation and the composition of the present oceanic crust

evolution of igneous rocks

composition of the mantle

conditions of pressure and temperature

Some of the major problems within the scope of igneous petrology are:

form and structure of igneous bodies

crystallization history of the minerals

classification of rocks

fractionation of parent magmas

mechanism of generation of magmas

history of formation and the composition of the present oceanic crust

evolution of igneous rocks

composition of the mantle

conditions of pressure and temperature

Sedimentary Petrology

The field of ___ is concerned with the description and classification of sedimentary rocks, interpretation of the processes of transportation and deposition of the sedimentary materials forming the rocks, the environment that prevailed at the time the sediments were deposited, and the alteration (compaction, cementation, and chemical and mineralogical modification) of the sediments after deposition.

Carbonate Petrology

Clastic Petrology

two main branches of sedimentary petrology

Carbonate Petrology

One branch deals with carbonate rocks, namely limestones and dolomites, composed principally of calcium carbonate (calcite) and calcium magnesium carbonate (dolomite).

Clastic Petrology

The other principal branch of sedimentary petrology is concerned with the sediments and sedimentary rocks that are essentially noncalcareous.

Carbonate Petrology

Much of the complexity in classifying carbonate rocks stems partly from the fact that many limestones and dolomites have been formed, directly or indirectly, through the influence of organisms, including bacteria, lime-secreting algae, various shelled organisms (e.g., mollusks and brachiopods), and by corals.

In limestones and dolomites that were deposited under marine conditions commonly in shallow warm seas, much of the material initially forming the rock consists of skeletons of lime-secreting organisms.

In many examples, this skeletal material is preserved as fossils.

Some of the major problems of carbonate petrology concern the physical and biological conditions of the environments in which carbonate material has been deposited, including water depth, temperature, degree of illumination by sunlight, motion by waves and currents, and the salinity and other chemical aspects of the water in which deposition occurred.

Clastic Petrology

These include sands and sandstones, clays and claystones, siltstones, conglomerates, glacial till, and varieties of sandstones, siltstones, and conglomerates (e.g., the graywacke-type sandstones and siltstones).

These rocks are broadly known as clastic rocks because they consist of distinct particles or clasts.

Clastic petrology is concerned with classification, particularly with respect to the mineral composition of fragments or particles, as well as the shapes of particles (angular versus rounded), and the degree of homogeneity of particle sizes.

Other main concerns of clastic petrology are the mode of transportation of sedimentary materials, including the transportation of clay, silt, and fine sand by wind; and the transportation of these and coarser materials through suspension in water, through traction by waves and currents in rivers, lakes, and seas, and sediment transport by ice.

Metamorphic Petrology

focuses on the composition and texture of metamorphic rocks (rocks such as slate, marble, gneiss, or schist which started out as sedimentary or igneous rocks but which have undergone chemical, mineralogical or textural changes due to extremes of pressure, temperature or both)

Metamorphism

means change in form

In geology the term is used to refer to a solid state recrystallization of earlier igneous, sedimentary, or metamorphic rocks.

Contact Metamorphism

Regional Metamorphism

two main types of metamorphism

Contact Metamorphism

in which changes induced largely by increase in temperature are localized at the contacts of igneous intrusions

Regional Metamorphism

in which increased pressure and temperature have caused recrystallization over extensive regions in mountain belts.

Metamorphism

Other types of ____ include local effects caused by deformation in fault zones, burning oil shales, and thrusted ophiolite complexes; extensive recrystallization caused by high heat flow in mid-ocean ridges; and shock metamorphism induced by high pressure pacts of meteorites and craters on the Earth and Moon.

Metamorphic Petrology is concerned with:

field relations and local tectonic environments;

the description and classification of metamorphic rocks in terms of their texture and chemistry, which provides information on the nature of the pre-metamorphic material;

the study of minerals and their chemistry (the mineral assemblages and their possible reactions), which yields data on the temperatures and pressures at which the rocks recrystallized; and

the study of fabrics and the relations of mineral growth to deformation stages and major structures, which provides information about the tectonic conditions under which regional metamorphic rocks formed.

Metamorphic Petrology is concerned with:

field relations and local tectonic environments;

the description and classification of metamorphic rocks in terms of their texture and chemistry, which provides information on the nature of the pre-metamorphic material;

the study of minerals and their chemistry (the mineral assemblages and their possible reactions), which yields data on the temperatures and pressures at which the rocks recrystallized; and

the study of fabrics and the relations of mineral growth to deformation stages and major structures, which provides information about the tectonic conditions under which regional metamorphic rocks formed.

Metasomatism

A supplement to metamorphism is ___: the introduction and expulsion of fluids and elements through rocks during recrystallization.

Rock Cycle

-States of Rock

Igneous

Metamorphic

Sedimentary

Magma

Sediment

-Changes of State of the Rock

Melting

Cooling

Heat and Pressure

Weathering and erosion

Compaction and cementation

Rock Cycle

-States of Rock

Igneous

Metamorphic

Sedimentary

Magma

Sediment

-Changes of State of the Rock

Melting

Cooling

Heat and Pressure

Weathering and erosion

Compaction and cementation

Devil's Tower National Monument

____ in Wyoming is an example of an igneous rock.

Igneous Rock

Rocks formed by the cooling and solidification of molten magma

They can have many different compositions, depending on the magma they cool from. They can also look different based on their cooling conditions.

Igneous rocks are grouped according to these

Chemical composition

Mode of occurrence

Mineralogy

Geometric setting of the ig ne ous structure

Texture

Chemical Classification

Felsic igneous rocks

Intermediate igneous rocks

Mafic igneous rocks

Ultramafic rock igneous rocks

Alkalic igneous rocks

Felsic igneous rocks

containing an excessive silica content, more than 63% SiO2 (examples granite and rhyolite)

Intermediate igneous rocks

containing among 52-63% SiO2 (example andesite and dacite)

Mafic igneous rocks

have low silica 45-52% and typically high iron - magnesium content material (example gabbro and basalt)

Ultramafic igneous rocks

with much less than 45% silica (examples picrite, komatiite and peridotite)

Alkalic igneous rocks

with 5-15% alkali (K2O + Na2O) content or with a molar ratio of alkali to silica extra than 1:6 (examples phonolite and trachyte)

Extrusive & Intrusive Igneous Rock

two main categories of igneous rocks:

Extrusive Igneous Rock

are formed on the surface of the Earth from lava, which is magma that has emerged from underground.

Intrusive Igneous Rock

Intrusive Igneous Rock are formed from magma that cools and solidifies within the crust of the planet

Intrusive Igneous Rock

also called plutonic rocks, cool slowly without ever reaching the surface

They have large crystals that are usually visible without a microscope. This surface is known as a phaneritic texture.

granite

Perhaps the best-known phaneritic rock is _____.

pegmatite

One extreme type of phaneritic rock is called____, found often in the U.S. state of Maine.

Pegmatite

____ can have a huge variety of crystal shapes and sizes, including some larger than a human hand.

Extrusive Igneous Rock

or volcanic igneous rock is produced when magma exits and cools above (or very near) the Earth's surface.

These are the rocks that form at erupting volcanoes and oozing fissures.

The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere.

Quick cooling

_____ means that mineral crystals don't have much time to grow, so these rocks have a very fine-grained or even glassy texture.

Hot gas bubbles are often trapped in the quenched lava, forming a bubbly, vesicular texture.

Aphanitic Texture

fine-grained

Rapid rate of surface cooling results in microscopic crystals

a sample is rhyolite, which has the same composition as granite

____ rocks may exhibit a secondary vesicular texture, like this basalt, as gas escaped from the lava.

Glassy Texture

This texture forms when lava from a volcanic eruption cools very rapidly such that no crystallization occurs.

This results in an amorphous glass that has little or no crystals. Obsidian and pumice rocks have this type of texture.

Pegmatitic Texture

This type of texture is formed when magma cools and some minerals increase in size extensively. The sizes may range from some centimeters to quite a number of meters. Pegmatite displays this texture.

Phaneritic Texture

This texture is seen in plutonic igneous rocks, which underwent slow crystallization underneath the surface of the earth.

When magma cools at a slow pace, the minerals are able to increase in size and have large crystals.

The crystals can be seen and distinguished by the naked eye.

Diorite, gabbro and granite possess this type of texture.

Porphyritic Texture

This texture is caused by the rapid change of conditions as the magma continues to cool down.

The ____ texture can also form when magma is crystallized under a volcano but eruption occurs before the crystallization is complete.

As a result, the lava formed crystallizes much faster with smaller-sized crystals.

Pyroclastic Texture

form when violent volcanic eruptions throw the lava into the atmosphere creating fragmental and glassy materials.

These materials eventually fall to the surface as lapilli, volcanic ash and volcanic bombs.

Andesite rock

is an igneous rock found on the Mayon Volcano, which is in the Philippines.

Rhyolite

is another type of igneous rock found on stratovolcanoes (like Mount Mayon). In color, ____ is light or almost white, with a lot of silica.

Geological Structure

Structures in the Earth's crust that have geological causes.

Structural geology

study of the processes that result in the formation of geologic structures and how these structures affect rocks.

Fault

Due to high pressure caused by tectonics

Tunnel, foundation, or slope construction

Fault Types

Dip-slip faults

Strike-slip faults

Oblique-slip faults

Dip-slip faults

movement parallel to the dip of the fault plane

Strike-slip faults

movement that is predominantly horizontal and parallel to the strike of the fault plane

Oblique-slip faults

movement with both vertical and horizontal components

Significance of Fault

Destruction of earth surface through earthquake

Lowers the stability of land

May play role in origin of earthquake and volcanism

May results thermal spring in particular area due to friction

Play role in soil formation through silicification and weathering

Fold

result of major tectonic forces

a stack of originally planar surfaces

form under varied conditions of stress, pore pressure, and temperature gradient

formed about the stress field

For Mining and Oil Industries

Crest plane

line that connects all crests.

Trough plane

line that connects all troughs

syncline

youngest ages in the centerline

anticline

oldest ages in the centerline

monocline

step-like fold

Significance of Fold

Shortening of Earth crust and their subsequent thickening

Usually stream follows from the axis of the anticline ridges

Dome structures occur along the axis of the syncline

Repetition of beds in their occurrence infers the presence of fold

May develop fractures and joints in anticline ridge

Joint

a break (fracture) of natural origin in a layer or body of rock most universal geologic structures

arise from a brittle fracture of a rock or layer due to tensile stress.

Important in developing natural resources, in the safe design of structures, and in environmental protection

Genetic & Geometric

Joint Classification

Genetic Classification

Tensional joint

Shear Joint

Tectonic joint

Tensional joint

a shrinkage joint

Shear Joint

developed from the sliding history of geological strata

Tectonic joint

developed from tectonic activities and categorized according to the attitude of beds.

Geometric classification

Strike joint

Dip joint

Oblique/diagonal joint

Significance of Joints

To understand the nature

Controls the drainage pattern.

May act as aquifers or reservoirs in rocks

Help to find out the brittle deformation in an area of construction

Finding out the trend and type of fractures and joints that host mineralization

Joints play a great role in soil formation

It lowers the stability of the land

Fold

permanent wavelike deformation in layered rock or sediment

Fault

fracture in bedrock along which rocks on one side have moved relative to the other side

Joint

fracture on a rock without noticeable movement

Result of Stress

Fold & Fault

Types of Fracture

Fault & Joint

Geologic Maps

shows the geological features of a certain region

Geologic Maps

1) Map

2) Explanation

3) Scale

4) Symbols

5) Correlation of map unit

Geologic Maps

Map Units

Contacts & Faults

Strike and Dip

Cross Section

Geologic Maps (Documents)

Well construction reports (WCRs)

Ground-penetrating radar (GPR)

Aeromagnetic and gravity surveys

Well logs

Rock cores

Putting the information together

Geologic Time

extensive interval of time occupied by the geologic history of Earth.

Geologic Time Scale

calendar for events in the history of Earth.

Geologic Time Scale Duration

eons

eras ('erathem')

periods

epochs

ages

eons

longest portions: Phanerozoic Eon, Proterozoic Eon, Archean Eon

eras ('erathem')

2nd longest portions: Eoarchean Era, Paleoarchean Era, Mesoarchean Era, Neoarchean Era, Paleoproterozoic Era, Mesoproterozoic Era, Neoproterozoic Era, Paleozoic Era, Mesozoic Era, Cenozoic Era

periods

basic unit during the time specific systems of rocks were formed

epochs

unit during which a rock series is deposited

45%

Soil Composition

Inorganic mineral matter: __%

25%

Soil Composition

Water: __%

25%

Soil Composition

Air: __%

5%

Soil Composition

Organic matter: __%

Organic matter

Includes humus/microorganisms and macroorganisms

Humus

dark organic material

Microorganisms

bacteria, etc.

Macroorganisms

earthworms, etc.