ESC Exam #3
laccolith
mass of magma that enters the Earth's crust and then solidifies, causing a deformation on the Earth's surface
sediment transport due to gravity
movement of sediments that occur on sloping surfaces in general, including hill slopes, scarps, cliffs, and the continental shelf—continental slope boundary (ocean floor).
lithification
part of diagenesis; the process in which sediments compact under pressure and gradually become solid rock; it includes all the processes which convert unconsolidated sediments to sedimentary rocks
igneous rock
rock formed of solidified magma
erosion
step 2 of formation of sedimentary rocks; the process of physically removing weathered materials
eon
two or more Eras; the largest division of geologic time
non-foliated metamorphic rock
type of metamorphic rock based on texture; formed around igneous intrusions where the temperatures are high but the pressures are relatively low and equal in all directions (confining pressure); identified on the basis of their composition. (EX: marble and quartzite which do not have a layered or banded appearance)
ore-forming minerals
type of mineral; those minerals that have a limited mode of occurrence or are formed by more unusual processes, such as the ores of metals, vein minerals, and cavity fillings
transparent
type of transparency; light can pass through the mineral and images can be seen clearly
translucent
type of transparency; light can pass through the mineral but is diffused so that images cannot be seen clearly
opaque
type of transparency; no light can pass through the mineral
the relative portion ratio of parent isotopes and daughter atoms
used to determine how many half-lives have passed since the formation of the mineral that contained the parent radioactive isotopes
quiescent
volcanos that are characterized by the calm, nonviolent extrusion of lava flows on the earth's surface
highly explosive
volcanos that are characterized by the violent ejection of fragmented volcanic debris, called tephra, which can extend tens of kilometers into the atmosphere above the volcano
what gives magma their explosive character
volume of gas expands as pressure is reduced; more violent eruptions occur where gases cannot escape easily
its temperature, composition, and gas content
what a magma's viscosity is largely controlled by
viscosity, composition and temperature of the magma
what controls the violence of volcanic eruptions
20
About 2,500 minerals are known to exist, but only about ___ are common in the crust.
metamorphic rocks
They are arise from the transformation of existing rock types, in a process. The original rock (protolith) is subjected to heat (temperatures greater than 150 or 200 °C) and pressure (1500 bars), causing profound physical and/or chemical change; The protolith may be sedimentary, igneous or another older metamorphic rock.
principle of superposition
a basic law of geochronology stating that in any undisturbed (not deformed) sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom; the same principle can be extended to many forms of volcanic igneous rocks
unconformity
a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous
index fossils
(also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages); They are species that existed for relatively short periods of geologic time and are found over large geographic areas; useful because their appearance in the rock record represents a specific time interval that scientists can use to readily identify and correlate rocks between different regions
three concepts in the study and use of fossils
Fossils represent the remains of once-living organisms. Most fossils are the remains of extinct organisms; that is, they belong to species that are no longer living anywhere on Earth. The kinds of fossils found in rocks of different ages differ because life on Earth has changed through time.
mineral it contains
The age of rock is considered as equivalent to the age of the ________
era
Two or more periods
crater
a circular depression in the ground caused by volcanic activity
conchoidal fracture
a curved breakage that resembles the concentric ripples of a mussel shell (quartz crystal)
quartzite
a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts
mineraloid
a mineral-like substance that does not demonstrate crystallinity
rock
a naturally occurring solid aggregate of one or more minerals or mineraloids
mineral
a naturally occurring substance that is solid and stable at room temperature, representable by a chemical formula, usually a biogenic, and has an ordered atomic structure (crystalline structure)
marble
a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite
magma
a silicate mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth; It is under very high pressure that can reach extremely high temperatures.
geologic time scale (GTS)
a system of chronological measurement that relates stratigraphy to time, and is used by geologists, paleontologists, and other earth scientists to describe the timing and relationships between events that have occurred throughout Earth's history
disconformity
a type of unconformity; between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition
nonconformity
a type of unconformity; exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock
angular unconformity
a type of unconformity; where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers
one; 50; 50
after ___ half-life, ___ percent of the parent remains, and the other ___ percent of the original atoms are converted to daughter atoms
two; 25; 75
after ___ half-lives, the number of parent isotopes is again halved (___ percent), and the number of daughter atoms increases by an equivalent amount (to ___ percent).
intrusive rock (plutonic rock)
an igneous rock that is crystallized from magma slowly cooling below the surface of the Earth at great depth (km or tens of km); characterized by large crystal size (their visual appearance shows individual crystals interlocked together to form the rock mass); course texture
ash layer
ash and lava form the layers that shape the volcano over time
cloud of volcanic ash
ash is formed of particles less than 2 mm in diameter; it is composed of pulverized magma and ground rock
principle of fossil succession
based on the appearance of fossils in sedimentary rocks. As organisms exist at the same time period throughout the world, their presence or (sometimes) absence may be used to provide a relative age of the formations in which they are found
principle of inclusions
can be applied to identify older pieces of rocks surrounded by younger igneous rocks; this law states that clasts in a rock are older than the rock itself.
clastic sediments
classification of sedimentary rocks based on the process that formed them; formed from the residues of weathering
chemical and biochemical precipitates
classification of sedimentary rocks based on the process that formed them; products of crystallization of ions that were dissolved during weathering
water vapor, carbon dioxide, and sulfur dioxide
common dissolved gases in magma
porphyritic texture
develops when slow cooling is followed by rapid cooling; phenocrysts surrounded by groundmass
extrusive rock (volcanic rock)
formed by the crystallization of magma at the surface of the Earth; characterized by fine-grained textures because their rapid cooling at or near the surface did not provide enough time for large crystals to grow
tephra
fragmented volcanic debris
geyser
hot water spring that ejects sporadic jets of water and vapor
more atoms
in the past there were (more or less) atoms of radioactive parent isotope of Uranium?
cemetation
involves ions carried in groundwater chemically precipitating to form new crystalline material within sediment pores. This is how "sediment" becomes "rock". The new pore-filling minerals form "bridges" between original sediment grains, thereby binding them together. So sand becomes "sandstone", and gravel becomes "conglomerate" or "breccia"
relative age
involves placing events in the order in which they occurred; it means describing the order or sequence of geologic events. Several rules or principles used to determine the sequence of geologic events are: original horizontality, superposition, cross-cutting relationships, lateral continuity and inclusions; the fossil record is also used to determine the order of events
crystalization
involves the arrangement of ions into an orderly atomic pattern
radiometric/radioactive dating
is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates; The principal source of information about the absolute age of rocks (igneous and metamorphic) and other geological features, including the age of the Earth itself
stable isotopes or stable nuclides
isotopes have never been observed to undergo radioactive decay
radioisotopes or radionuclides
isotopes that are radioactive
main vent
it is the main channel through which the hot magma moves to reach the Earth's surface
phenocrysts
large crystals
lava flow
lava mass pouring from a volcano at average speeds of 0.083 m/s; it can reach temperatures as high as 1,200°C
sill
layer of magma that has solidified between the layers of the Earth's crust
lava layer
layer of volcanic rock formed by cooled lava
volcanic bomb
mass of magma ejected high into the air where it solidifies; it can be very large
dike
mass of magma that enters the Earth's crust and then solidifies in the form of blade-like shafts that are vertical or oblique to the layers of the Earth.
retrograde metamorphism
metamorphism produced with decreasing temperatures and pressure
prograde metamorphism
metamorphism produced with increasing pressure and temperature conditions
sediment transport due to fluid motion
movement of sediments that occurs in rivers, oceans, lakes, seas, and other bodies of water due to currents and tides
sediments
particles that form a sedimentary rock by accumulating
streak
physical property of a mineral; (aka powder color) the color of the powder produced when the mineral is dragged across an unweathered surface
hardness
physical property of a mineral; The Mohs Scale characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material
tenacity
physical property of a mineral; a mineral's physical reaction to stressful forces acting upon it; these forces may include, but are not limited to: breaking, tearing, crushing, or bending; generally classified into categories: brittle, malleable, and flexible.
transparency
physical property of a mineral; refers to the degree to which light can pass through a mineral
fracture
physical property of a mineral; the shape and texture of the surface formed when a mineral is fractured
cleavage
physical property of a mineral; the tendency of a mineral to break along flat planar surfaces as determined by the structure of its crystal lattice; the way a mineral breaks
lustre
physical property of a mineral; the way light interacts with the surface of a crystal, rock, or mineral; categorized as: metallic, greasy, glassy and silky.
magma chamber
pocket where magma accumulates before rising to the surface
pyroclastic flow
product of volcanic eruption; a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed
lahar
product of volcanic eruption; a destructive mudflow on the slopes of a volcano
eruption cloud
product of volcanic eruption; cloud of hot volcanic ash suspended in volcanic gas emitted during an explosive volcanic eruption
acid rain
product of volcanic eruption; rainfall made sufficiently acidic by atmospheric pollution that it causes environmental harm
principle of original horizontality
proposed by the Danish geological pioneer Nicholas Steno (1638-1686); This principle states that layers of sediment are originally deposited horizontally under the action of gravity. The principle is important to the analysis of folded and tilted strata; it is the geologists' first rule for reconstructing Earth's timescale.
absolute age
provides a computed numerical age in contrast with relative dating which provides only an order of events or geological processes; the age of a rock unit, fossil or geologic event expressed in units of time, such as years or million years
the study of metamorphic rocks
provides information about the temperatures and pressures that occur at great depths within the Earth's crust
sedimentary
radiometric dating is least useful for ___________ rocks.
fumarole
regular emission of gas from a fissure on the Earth's surface
gas escapes easy from low viscosity
relationship between gases escaping and viscosity
viscosity increases, temperate decreases, gases low
relationship between magma's temp and viscosity and gas content
higher silica, higher viscosity
relationship between silica content and viscosity
shale, slate, phyllite, schist, and gneiss
rock types arranged in increasing metamorphism
bedding
sedimentary rocks are deposited in layers as strata, forming a structure called _________; layers can be readily identified in nature on the basis of different colors, thicknesses, and resistance to erosion, properties that are linked to the composition and origin of the rocks
matrix or groundmass
small crystals
side vent
small rise that appears on the side of the volcano and is fed by the main vent
epochs
some periods are divided into _____
principle of lateral continuity
states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous; As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.
principle of cross-cutting relationships
states that older rocks may be cut by younger rocks or other geologic features.
weathering
step 1 of formation of sedimentary rocks; the slow changes that result in the breaking up, the crumbling, and the destruction of any kind of solid rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere
sediment transport
step 3 of formation of sedimentary rocks; the movement of solid particles, typically due to a combination of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained; occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; also caused by glaciers as they flow, and on terrestrial surfaces under the influence of wind.
deposition (sedimentation)
step 4 of formation of sedimentary rocks; occurs when particles settle out or dissolved minerals precipitate
burial
step 5 of formation of sedimentary rocks; occurs as layers accumulate and compact previous layers
diagenesis
step 6 of the process of formation of sedimentary rocks; involves pressure, heat, and chemical reactions, lithifies the sediment to make sedimentary rocks
isostasy
term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density
phaneritic texture
term usually used to refer to igneous rock grain size; it means that the size of matrix grains in the rock are large enough to be distinguished with the unaided eye
period
the basic unit of geological time in which a single type of rock system is formed
metamorphism
the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change); The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids usually while buried deep below Earth's surface; Depending on the combination of pressure, temperature, an the chemical composition of circulating fluids, one rock has the potential to be converted into several different metamorphic rock types
the study of the sequence of sedimentary rock strata
the main source for scientific knowledge about the Earth's history, including paleogeography, paleoclimatology and the history of life
volcanism
the phenomenon of eruption of molten rock (magma) onto the surface of the Earth, where lava, pyroclastic and volcanic gases erupt through a break in the surface called a vent; includes all phenomena resulting from and causing magma within the crust or mantle of the body to rise through the crust and form volcanic rocks on the surface
the internal heat of the Earth, the weight of overlying rocks, and horizontal pressures developed as rocks become deformed
the pressure and heat that drive metamorphism result from which three forces?
daughter isotope
the product of the isotope decay; may be another radioactive isotope or an atom that is stable; Radioactive decay starts and these atoms begin to accumulate in rocks as soon as a mineral forms.
viscosity
the resistance to flow
radioactive decay
the spontaneous transformation of an unstable atomic nucleus into a lighter one, in which radiation is released in form of alpha particles, beta particles, gamma rays, and other particles; The positively charged protons in a nucleus repel each other, tending to make the nucleus unstable; occurs when an unstable isotope changes to a new element as a result of the emission or capture of subatomic particles (protons, neutrons, electrons).
faunal succession
the study of _____ allows matching of similarly-aged rocks from different outcrops
volcanology
the study of volcanoes, lava, magma, and related geological, geophysical and geochemical phenomena
law of fossil succession
the three concepts are summarized in a general principle; states that the kinds of animals and plants found as fossils change through time. When we find the same kinds of fossils in rocks from different places, we know that the rocks are the same age.
half-life
the time taken for half of the parent isotope to convert to daughter atoms
parent isotope
the unstable original isotope
magma crystalization
this process occurs because of temperature decreases as the magma rises to the surface; as the magma starts to cools, it will start to grow crystals; form different groups of minerals (rock forming minerals)
foliated metamorphic rock
type of metamorphic rock based on texture; such as gneiss, phyllite, schist and slate which have a layered or banded appearance that is produced by exposure to heat and directed pressure; Minerals are aligned parallel to each other and perpendicular to the direction of pressure
regional metamorphism
type of metamorphism that covers large areas of continental crust typically associated with mountain ranges, particularly those associated with convergent tectonic plates or the roots of previously eroded mountains; rocks that form closer to the margin of the tectonic plates, where the heat and pressure are greatest, often differ in their minerals and texture from those that form farther away
contact metamorphism
type of metamorphism that occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock; The area surrounding the intrusion is called the metamorphic aureole
rock-forming minerals
type of mineral; minerals that form igneous, sedimentary, or metamorphic rocks and that typically, or solely, form as an intimate part of rock-making processes
alteration minerals (secondary minerals)
type of mineral; not properly classified as rock-forming minerals. They form at a later time than the original rock and tend to destroy its original character.
dormant volcano
type of volcano based on activity; is an active volcano that is not erupting, but supposed to erupt again
active volcano
type of volcano based on activity; most scientists consider this type of volcano if it has erupted in the last 10,000 years. There are about 1500 of these volcanoes in the world - the majority along the Pacific Ring of Fire - and around 50 of these erupt each year
extinct volcano
type of volcano based on activity; that which scientists consider unlikely to erupt again, because the volcano no longer has a magma supply; has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future
caldera
type of volcano based on landform; a crater that forms when a stratovolcano or shield volcano collapses into a shallow and empty magma chamber below the volcano; tends to be highly explosive; high viscosity
stratovolcano (composite volcano)
type of volcano based on landform; is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash; a majority of the world's active volcanoes and form on convergent plate boundaries; have a violent style of eruption that blasts debris several kilometer into the atmosphere; high viscosity
shield volcanos
type of volcano based on landform; it is characterized by gentle sloping sides built up from thousands of fluid, low-viscosity lava flow; gentle lava flow/eruption
cinder cone volcano (scoria cone)
type of volcano based on landform; steep conical hill of tephra (volcanic debris) that accumulates around and downwind from a volcanic vent; quiet eruption
sedimentary rocks
types of rock that are formed by the deposition of material at the Earth's surface, near the surface and/or within bodies of water (oceans, rivers, lakes); they are formed by weathering, erosion, transportation, deposition and diagenesis
maximum temperature for metamorphism
typically 700-900 degrees celsius depending on the pressure and on the composition of the rock
aphanitic texture
typically form from lava which crystallize rapidly on or near the Earth' surface; The individual crystals are not distinguishable to the naked eye
