Term
| What 3 Criteria must a substance meet to be a mineral? |
|
Definition
-naturally occurring
-definable chemical composition
-internal structure characterized by an orderly arrangement of atoms in a crystalline structure |
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Term
| Why is the total number of common minerals fairly small? |
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Definition
not that many elements are abundant --> we only have 8 common elements
elements have to be combined in certain ratios and formations, so the possibilities are few |
|
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Term
|
Definition
-ides: consist of a single type of anion bonded to at least one type of cation
-ates: consist of a complex anion (single type of cation + oxygen) bonded with at least one type of cation |
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Term
| What is the basic building block of silicate minerals? |
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Definition
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Term
| What makes physical weathering happen? |
|
Definition
-physical abrasion (from ice, liquid water, or wind)
-crystals grow in water--> ice forms in rocks, expands & cracks rocks (frost wedging)
-salt wedging: salt crystals grow, expand & crack rocks
-thermal expansion: expansion & contraction due to change in temp causes cracks
-animals & humans |
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Term
| What makes chemical weathering happen? Why is rain a more effective agent of chemical weathering than pure H2O? |
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Definition
-rain turns acidic & erodes rocks
-groundwater erosion |
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Term
| How do Al-bearing and Al-free minerals dissolve differently, and how is this reflecting in the type of sediment produced? |
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Definition
| Al-free minerals dissolve completely, without a trace (called congruent dissolution). Al-bearing minerals leave a residue of silicate clays (called incongruent dissolution). If we see a silicate clay, we know that it is probably the trace left from a dissolved mineral |
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Term
| What roles to organisms play in weathering? |
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Definition
-plants create higher acidity in water, increasing chemical weathering from groundwater
-root wedging
-plants stabilize the ground, preventing erosion
-organisms such as termites can burrow, creating weathering |
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Term
| What do soils consist of? |
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Definition
| organic material, minerals, clay, broken rock |
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Term
| What are the main horizons in a mature soil profile and what distinguishes one horizon from another? |
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Definition
-O (organic): humus
-A (topsoil): biological activity
-B (subsoil): clay made from materials leached from above |
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Term
| What processes make soil horizons develop over time? |
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Definition
| Organic material decays on surface. rain falls, rocks on surface are weathered, and ions are removed from A zone, then accumulate in B zone. |
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Term
| How do (sili)clastic vs. chemical sediments differ in origin? |
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Definition
| Siliclastic rocks are made up of fragments and grain from preexisting rocks, whereas chemical sediments from from minerals precipitated from groundwater. |
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Term
| Via what media and mechanisms are sediments commonly transported? |
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Definition
Wind (sand, dust)
Water (rivers-- pebbles,s small rock, glaciers--unsorted material, etc)
Mass movements |
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Term
| How are different modes of transportation reflected in the sizes, shapes, sorting, and/or structures of sediments after they come to rest? |
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Definition
- Smaller, more rounded sediments show that clasts have traveled far, and probably from streams
- Unsorted material comes from glaciers or mass movements
- larger clasts require more energy to transport
angular shards are close to source
- layers of dust and sand could be from wind or slow moving streams
- Well sorted material comes from streams & moving water, or from wind power
- structures show type and chronology of transportation -- layers show different modes of transportation ie. sand dunes with cross beds show spurts of movement from winds
- ripple marks show water or wind movement
- elongated ridges tell us direction of flow
siliciclastic sedimentary rocks show that clasts of rocks were carried away and formed into a sediment later |
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Term
| What criteria are used to distinguish one surface environment from another? |
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Definition
topography of the land
sorting of sediments
surface markings (mud cracks, scour marks, fossils)
glacial: unsorted, unstratified
mountain stream: coarse conglomerates w/ larger & smaller clasts
alluvial fans: sand & smaller grains
sand dunes: well sorted sand --> sandstone w/ cross beds
lake environments: coarse sediment near shore, clay in center --> finely laminated shale
rivers: sand, silt, mud --> creates floodplains w/ mud layers & mud cracks |
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Term
| How do erosional environments differ from depositional environments? |
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Definition
| erosional environments are more variant and hilly than depositional ones, which tend to be more flat (erosion creates valleys, deposition fills them in) |
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Term
| What is a sedimentary facies, and what clues can be used to determine the environment in which it was originally deposited? |
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Definition
| a sedimentary facies is a group of rocks and primary structures indicative of a given depositional environment |
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Term
| Via what processes can loose sediments be converted to solid rock given lots of time? |
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Definition
clasts can be lithified by compaction and cementation over time
shells and plant material can be compacted and mixed with mud to create sediments
evaporites are formed when saltwater evaporates
minerals precipitating from groundwater |
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Term
| What sorts of records of prehistoric life have survived to the present day? |
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Definition
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Term
| How have records of prehistoric life been used to measure relative time in prehistoric strata? |
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Definition
| fossils found in the geologic column can be dated relative to crystals found (that can be dated by radioactive carbon dating). The law of faunal succession tells us that fossils that are in bottom layers are older than those above them, which helps us determine relative age. |
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Term
| What methods were used to estimate the actual duration of geologic time prior to and during the 1800's? |
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Definition
-Geneology of the Bible
-determine how old the earth is by figuring out how long it would have taken for the earth to cool from being molten lava to present day
-figure out how long it takes to deposit a foot of sediment, and then how many feet of sediment there are on the earth |
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Term
| How can you determine the absolute age of a given crystal? What assumptions do you have to make? |
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Definition
| You can date crystals using knowledge of the half lives of the radioactive isotopes in the crystals. You have to assume that the radioactive material was always in the crystal |
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Term
| What types of crystals work best for age dating? |
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Definition
| crystals that contain radioactive material, from being formed during the cooling of magma in the making of igneous rock |
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Term
| How can crystals be used to constrain the absolute ages of time periods in the geologic column? |
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Definition
| crystals that contain radioactive isotopes can be dated exactly. If we know the age of crystals in the geologic column, we can assign an age to the part of the column that the crystal came from. |
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Term
|
Definition
|
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Term
| When did dinosaurs exist? |
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Definition
|
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Term
What are the three main types of volcanic eruption?
What characteristics do the products of each style of eruption have? |
|
Definition
lava flow (molten or solid lava)
pyroclastic fall:nbroken fragments, ash & tephra falls -> creates layers over time; sorts & stratifies
pyroclastic flow: mass movement, hot & fast, poorly sorted & unstratified |
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Term
| Why do volcanic eruptions occur? |
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Definition
| Earth's mantle (made of solid rock) melts and rises. Gas bubbles form and create pressure, which cause pyroclastic explosions |
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Term
| Why are some eruptions more explosive than others? |
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Definition
| Some types of lava are more viscous than others. Bubbles are unable to pop in very viscous lava, so the pressure builds up, creating a big eruption |
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Term
| What are the main types of volcanic edifices, and what types of magma and eruptions are associated with each? |
|
Definition
Shield volcanoes: broad, gentle domes caused by low viscosity basaltic lava or pyroclastic sheets
Stratovolcanoes: steep cones, made from lava flows, pyroclastic flows & pyroclastic falls --> layered (form on subduction zones) |
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Term
| What happens to magma that gets stuck underground? |
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Definition
| Magma that gets stuck underground cools, forming igneous rock (plutons) |
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Term
| How can you tell that a body of rock formed as an intrusion (pluton) long after it cools off? |
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Definition
often, intrusions of magma into solid rock affect the surrounding rock (get darker at "alteration zones")
Also, sometimes xenoliths (broken pieces) get engulfed in the intruding rock and get carried away (not far). If you see xenoliths, you know you are dealing with an intrusion. |
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Term
| What are the 2 main chemical elements in a normal magma? |
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Definition
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Term
| When you melt part of a rock, how does the composition of the melt differ from what you started with? |
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Definition
| melted rock is higher in silica than solid rock |
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Term
| What direct hazards are associated with different types of volcanoes and eruptions? |
|
Definition
-Lavas: property damage
-pyroclastic falls: respiratory problems and roof damage from ash, ballistic impact from huge falling pieces, problems with planes
-pyroclastic flow: most dangerous to life and limb- will burn and kill you if you come in contact with it (also very hot gas) |
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Term
| What indirect hazards are associated with different types of volcanoes and eruptions? |
|
Definition
-lahars: volcanic debris flows (same hazards as other mass movements)
-tsunamis: caused by raise in sea level
-fine ash/aerosols caused by pyroclastic flows & expecially falls block sunlight and cool surface temp of earch |
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Term
| Via what methods can the likelihood that a volcanic eruption will take place in the future be assessed? |
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Definition
-determine how often they erupt and predict when the next one will be
-delineate hazard zones
-predict imminent volcano eruptions and evacuate (precursor phenomena: earthquakes, inflation of volcano (monitored by tiltmeter), gas release) |
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Term
| What can humans do to minimize volcanic hazards? |
|
Definition
-build shelters
-cool lava with water to harden it and divert the flow
-build 'dams' to slow/stop debris from lahars
-build observatories |
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Term
| How does stress differ from strain? |
|
Definition
Stress creates strain
stress can be applied, but if the material is elastic, it will return to its original shape. Strain is a force that changes the shape of a material irrevocably.
Stress is force applied, strain is the result. |
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Term
| How does the way a rock changes differ if the deformation is brittle vs. ductile? |
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Definition
| brittle rocks fracture and break, while ductile rocks bend and flow |
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Term
| How do the 3 main types of faults generally match up with the 2 types of plate margins? |
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Definition
-strike slip faults occur at active continental plate margins
-normal faults & rifts occur at mid ocean ridges/ divergent plate margins
-reverse faulting occurs at convergent margins |
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|
Term
| On which type of plate margin are most folds found? |
|
Definition
| most folds are found at convergent margins |
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Term
|
Definition
| ion/group of ions with a positive charge |
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Term
|
Definition
| ion/group of ions with a negative charge |
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Term
|
Definition
| a measure of the number of chemical bonds formed by the atoms of a given element. |
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Term
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Definition
| The replacement of one type of ion in a mineral by another that is similar to the first in size and charge. |
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Term
|
Definition
| 2 different minerals with the same chemical composition, but different crystal structures |
|
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Term
|
Definition
| SiO4 : one silica fits in between 4 oxygen, creating a tetrahedron shape |
|
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Term
|
Definition
KAlSi3O3
most common mineral in granite |
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Term
|
Definition
Ca2SiO4 rock that makes up most of the earth's mantle
island silicate: molecules floating around cations) |
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Term
|
Definition
| rocks containing calcite and/or dolomite |
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Term
|
Definition
| the process by which water trapped in joints freezes and expands, pushing the joints open, and sometimes increasing their size |
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Term
|
Definition
| the process in arid climates by which dissolved salt in groundwater crystallizes and grows in open pore spaces in rocks and pushes apart the surrounding grains |
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Term
|
Definition
| The repeated cooling and heating of rocks causes rocks to repeatedly shrink and expand. This eventually causes fractures and weaknesses in the rock |
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Term
|
Definition
| to leach: to dissolve and carry away |
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Term
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Definition
| When a mineral dissolves, but leaves a sediment of silicate clay behind of particles that couldn't dissolve (Al) |
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Term
|
Definition
| The unconsolidated mineral or organic material from which the true soil develops |
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Term
|
Definition
|
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Term
|
Definition
| a layer of rotten rock created by chemical weathering in warm, wet climates |
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Term
|
Definition
| Chemical weathering in which concentric or spherical shells of decayed rock are successively separated from a block of rock; commonly results in the formation of a rounded boulder of decomposition. |
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Term
|
Definition
| top layer; consists almost entirely of organic matter and almost no mineral matter |
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Term
|
Definition
The amorphous, ordinarily dark-colored, colloidal matter in soil; a complex of the fractions of organic matter of plant, animal, and microbial origin that are most resistant to decomposition.
Organic matter that has been converted, not decayed. |
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Term
|
Definition
| below o horizon; dark grey to blackish brown topsoil; humus has decayed further, and has mixed with mineral grains. water percolates through a horizon and produces ions and new clay materials |
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Term
|
Definition
| below a horizon; soil that has undergone substantial leaching but has not yet mixed with organic material; lighter in color than the a horizon |
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Term
|
Definition
| subsoil: ions and clay accumulate (zone of accumulation) |
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Term
|
Definition
| material derived from substrate that has been chemically weathered and broken apart, but has not yet undergone leaching or accumulation |
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Term
|
Definition
| contains grains and clasts that are larger than 2mm in diameter |
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Term
|
Definition
| contains grains that are between 1/16mm and 2mm in diameter |
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Term
|
Definition
| contains grains that are too small to be seen |
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Term
|
Definition
| wave ripple marks are small, elongated ridges with even sides/ faces |
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Term
|
Definition
| current ripple marks are small, elongated ridges with uneven sides. Not as uniform as wave ripple marks-- occur in more sporadic formations, like sand dunes |
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Term
|
Definition
| cross beds are internal laminations within rocks that show different layers of sediment deposited over time |
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Term
|
Definition
| if a layer of mud dries up after deposition, it cracks into roughly hexagonal plates that typically curl up at their edges. |
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Term
|
Definition
| any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering) and metamorphism |
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Term
|
Definition
| the transformation of loose sediment into solid rock through compaction and cementation |
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Term
|
Definition
| the phase of lithification in which the pressure of the overburden on the buried rock squeezes out water and air that was trapped between clasts, and the clasts press tightly together |
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Term
|
Definition
| the phase of lithification in which cement, consisting of minerals that precipitate from groundwater, partially or completely fills the spaces between clasts and attaches each grain to its neighbor |
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Term
|
Definition
| the replacement of minerals with other minerals, one ion at a time, through precipitation from groundwater |
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Term
|
Definition
| A fossil exhibiting evidence of an organism, but not the organism itself. Example: footprints in rock. |
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Term
| body fossil / "hard parts" |
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Definition
| A fossil of an entire body of an organism |
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Term
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Definition
| the fossilization process in which plant material becomes transformed into rock by the precipitation of silica from groundwater. |
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Term
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Definition
| a cast/mold is created when minerals precipitate out of groundwater, and form a rock around an organism. The organism then decays, leaving the mold of its body. |
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Term
|
Definition
| removing everything from living organisms except for carbon --> common mode of fossilization |
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Term
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Definition
| English geologist who made the first geologic map in the later 1700's |
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Term
|
Definition
| The law that things that are in layers are organized chronologically --> layers at bottom are older than layers on top |
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Term
|
Definition
| when vast numbers of species abruptly vanish |
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Term
|
Definition
| a boundary between two different rock sequences representing an interval of time during which new strata were not deposited and/or were eroded |
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Term
|
Definition
| The Scottish geologist who came up with the idea of uniformitarianism in the 1700's |
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Term
|
Definition
| uniformitarianism assumes that the same natural laws and processes that operate in the universe now, have always operated in the universe in the past and apply everywhere in the universe. It is frequently summarized as "the present is the key to the past," because it holds that all things continue as they were from the beginning of the world. |
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Term
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Definition
| The amount of sediment accumulated in an environment over a given period of time, usually expressed as thickness of accumulation per unit time |
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Term
|
Definition
| ancient soil preserved in the stratigraphic record |
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Term
|
Definition
| earth is cooling off. Geologists tried to use this theory to date the earth (but forgot that the earth was also creating heat simultaneously) |
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Term
|
Definition
| Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting ionizing particles (ionizing radiation) |
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Term
|
Definition
| A parent isotope is a radioactive isotope that undergoes decay |
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Term
|
Definition
| the time it takes for 1/2 of a radioactive substance to decay |
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Term
|
Definition
| what is left after a parent isotope undergoes radioactive decay |
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Term
| cross-cutting relationships |
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Definition
| The law that says that things that break other things are younger. Things that are broken by other things must be older than the things that broke them. |
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Term
|
Definition
Age of mammals
65 million years ago to the present |
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Term
|
Definition
Age of Dinosaurs
between 250 and 65 million years ago |
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Term
|
Definition
| 542-251 million years ago |
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Term
|
Definition
| from beginning of earth to beginning of cambrian era (542 million years ago) |
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Term
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Definition
| sheets or mounds of lava that flow onto the ground surface or sea floor in molten form and then solidify |
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Term
|
Definition
| a lava flow with a surface texture of smooth, glassy, rope-like ridges |
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Term
|
Definition
| a lava flow with a rubbly surface |
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Term
|
Definition
| (pillow basalt) glass-encrusted basalt blobs that form when magma extrudes on the sea floor and cools very quickly |
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Term
| pyroclastic (or air) fall |
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Definition
|
|
Term
| pyroclastic (or ash) flow |
|
Definition
| a fast-moving avalanche that occurs when hot volcanic ash and debris mix with air and flow down the side of a volcano |
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Term
|
Definition
| unconsolidated accumulations of pyroclastic grains |
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Term
|
Definition
| the material left over after bubbles pop; if bubbles are highly concentrated, they pop, and their "shells" harden quickly and turn into glass shards |
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Term
|
Definition
| ash and debris from a pyroclastic fall create an even bedding over everything |
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Term
|
Definition
| when big particles fall at the bottom and small particles fall on top |
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Term
|
Definition
| the ability of an object to float |
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Term
|
Definition
| the formation of gas bubbles in lava as it melts and expands |
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Term
|
Definition
| open holes in igneous rock formed by the preservation of bubbles in magma as the magma cools into solid rock |
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Term
|
Definition
| a subaerial volcano with a broad, gentle dome, formed either from low-viscosity basaltic lava or from large pyroclastic sheets |
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Term
|
Definition
| a large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra |
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Term
|
Definition
| a large circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below |
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Term
|
Definition
| when lava erupts out of a conduit in a magma chamber in the shape of a long crack |
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Term
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Definition
| vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has low viscocity |
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Term
|
Definition
| a dome-like mass of rhyolitic lava that accumulates above the eruption vent |
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Term
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Definition
| the measure of a liquid's ability to flow. A highly viscous liquid doesn't flow very easily, whereas a liquid with low viscosity flows easily |
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Term
|
Definition
| a fine-grained mafic (poor in silica, rich in Fe & Mg) igneous rock |
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Term
|
Definition
| lava with a medium amount of silica (60%), and medium viscocity (between basalt and rhyolite) also not as hot as basalt |
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Term
|
Definition
rock that is buried deep in the ground is put under pressure. When buried rock rises, temperature doesn't change, but pressure does. This turns solid into liquid. This is what happens to mantle as it rises and turns into magma.
--> occurs at mid ocean ridges and causes sea flood spreading |
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Term
|
Definition
| a space below ground filled with magma |
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Term
|
Definition
| a wall-shaped intrusion of rock that cuts across the layering of country rock |
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Term
|
Definition
| a nearly horizontal table-top-shaped tabular intrusion that occurs between the layers of country rock |
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Term
|
Definition
| a stock is a discordant igneous intrusion having a surface exposure of less than 40 sq mi. Differs from a batholith only in being smaller |
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Term
|
Definition
| a vast composite, intrusive, igneous rock body up to several hundred km long and 100 km wide, formed by the intrusion of numerous plutons in the same region |
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Term
|
Definition
| a thick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the flank of a volcano |
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Term
|
Definition
| large waves that are created by a rise in sea level (often caused by volcanic eruptions and related earthquakes) |
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Term
|
Definition
| things that happen before volcanic eruptions: earthquakes, tilt of volcano increasing due to "inflation", and gas emission |
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Term
|
Definition
| a device used to predict volcanoes by measuring the tilt of the volcano (tilt increases before an eruption) |
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Term
|
Definition
| a way to predict volcanoes by monitoring seismic activity (earthquakes occur before eruptions) |
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Term
|
Definition
| volcanoes emit gas before they erupt. monitoring gas levels in the air can help us predict volcanoes |
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Term
|
Definition
| When a material is deformed by stress, but not broken. Elastic materials are able to return to their previous shapes after they are deformed. |
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|
Term
| strike-slip or transform fault |
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Definition
| a fault marking a transform plate boundary; along mid-ocean ridges, transform faults are the actively slipping segment of a fracture zone between two ridge segments |
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Term
|
Definition
| a fractur on which one body of rock slides past another |
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Term
|
Definition
| a steeply dipping fault on which the hanging-wall block slides up |
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|
Term
|
Definition
| a fold with an arch-like shape in which the limbs dip away from the hinge |
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|
Term
|
Definition
| a trough-shaped fold whose limbs dip toward the hinge |
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