Earth Science Regents review 2
James Hutton
" the father of geology" Coined the phrase "the present is the key to the past"
Mesozoic Era
"age of reptiles" 3 Periods Triassic Jurassic Cretaceous
Material is "ductile"
"bends" typical under high heat and pressure, long periods of stress
faulting material
"breaks" typical near the surface, due to short, abrupt periods of stress
Criteria for index fossils, in order to be an index fossil, the fossil must
Be scattered over a large geographic area (widespread) Have features that distinguish it from other fossils Have lived during a (geologically) short period of time (short lived) (millions of years) Be widely distributed within a rock layer
Life of the Paleozoic era (oldest to youngest)
Cambrian explosion of animals with skeletons Ordovician first invertebrates appear
Index fossil
Can be used to correlate sedimentary rock layers relative age to one another
why is color an unreliable clue to the identity of a mineral
Color alone is not usually reliable for identifying minerals because many minerals are similar in color and very small amounts of certain elements can greatly affect the color of a mineral
silicate
Combination of silicone and oxygen
Mineral Hardness Field Tests
Fingernail scratches <2.5 Copper Coin scratches < 3.5 glass scratches < 5.5 Steel scratches <6.5
Jurassic
First birds First placental mammals
Triassic
First dinosaurs Pangaea begins to break up Earliest mammals
Cretaceous
First flowering plants Extinction of dinosaurs ammonoids and many land plants
special properties that may help identify certain minerals
Fluorescence and Phosphorescence Chatoyancy (Cat's- eye effect) Asterism Double refraction Magnetism Radioactivity
Intrusive
Form inside the Earth Coarse grained Form from pressure inside the Earth Granite, diorite, gabbro, peridotite
Extrusive
Form outside /on the Earth's surface Fine grained Come from volcanoes or cracks in the Earth Obsidian, basalt, pumice, scoria, vesicular rhyodite
Metamorphic rocks
Formed from other rocks through metamorphism caused by heat and pressure
Precambrian time
Fossils are rare in Precambrian rock mostly b/c Precambrian life lacked exoskeleton Stromatolites are one of the few Precambrian fossils discovered
Felsic
Generally light in color Lower in density
atoms change from unstable to stable this happens over a specific period of time called
Half-life This assumption allows us to date rocks
Mafic
High density Dark color
Causes of regional metamorphism
High tectonic activity from plates colliding, splitting apart, or gliding past each other The more heat and pressure you add to the rock, the more it metamorphoses When rock is subducted into the Earth's crust, the entire area gets heated up and placed under greater pressure as rocks collide and as some dive into the Earth.
characteristics that are necessary to classify a substance as a mineral
Inorganic not made up of living things or the remains of living things Occurs naturally Crystalline solid Consistent chemical composition
To verify a mineral
Is it organic? Does it occur naturally? Is the substance a solid in crystalline form? (Is it a crystalline solid?) Does it have a consistent chemical composition?
Felsic
Lighter color less dense Si and Al rich
Paleozoic era
because of the rich fossil record, the has been divided into 7 periods the periods are named after geographic locations
Fracture
break unevenly into pieces that have curved or irregular surfaces.
Color
but color alone is not usually very reliable
Contact
caused mostly by heat rocks can be either high or low grade metamorphism
Intense heat from magma source
changes the structure and mineral composition of the surrounding rock
Bioclastic
chemical sedimentary rocks
Mafic
darker color more dense Fe and Mg rich
When sediment transport stops this is called
deposition
Color
determined by the elements that make up the mineral and how they interact with light
non-silicate
does not contain silicone and oxygen
Non-metallic
doesn't appear as a polished metal
The majority of Earth is made up of 2 elements
oxygen and silicon. Oxygen and silicon make up silicate minerals
earliest grasses
paleogene
Slaty foliation
parallel alignment of minerals into layers
Relative dating
qualitative (ie numbers) age determination of rock or events relative to other rocks or events
humans, mammoths, mastodonts
quarternary
Geiger counter is used to measure
radioactivity in a mineral
Two different types of metamorphism
regional contact
Paleontologists can use fossils to determine
relative age of a rock
Different kinds of bonds
have different strengths
Regional
heat and pressure over large areas
Strain
how a material responds to stress
Hardness of a mineral is determined by
how strong the bond between the atoms is
Superposition
in undisturbed layers of rock the youngest layer is found on top and the oldest is found on the bottom.
Intrusive
injected and cooled underground as magma
3 different types of sedimentary rocks
inorganic (clastic) chemical organic
Two types of igneous rocks
intrusive extrusive
Mafic
is a word derived from magnesium and ferric (iron) because the minerals from which mafic rocks form are rich in iron and magnesium.
Radiometric Dating
is the name given to the technique for determining the exact (absolute age) age of a rock.
When the water in large lakes evaporates
it leaves behind minerals
Luster
light that is reflected from the minerals surface Cleavage and fracture
Felsic vs. mafic
look at ESRT Sheme for igneous rock identification
Sediment
loose fragments of rock, minerals and organic material resulting from a natural process
Nonfoliated
made mostly of a single individual material causing it to be one color
Clastic (fragmental) sedimentary rocks
made up of different sized particles or sediments that have been compressed and/or cemented together classified by the size of their sediments or grains Shale has the smallest particle (clay) and conglomerate is a mixture of all the different particle sizes
Only rocks can be
mafic or felsic not minerals the minerals on the bottom of scheme/igneous rock ID are neither felsic or mafic because they are minerals Only rocks can be mafic or felsic!!!!
Compression
material is "pressed" together
Tension
material is pulled apart
Shear
material is torn horizontally moving in opposite directions
As heat and pressure increase
metamorphism increases
Luster
the light that is reflected from a minerals surface
what is the ratio of Carbon 14 to Nitrogen 14 after 3 half lives have passed?
12.5/87.5
Multiple minerals make up small rocks
2 + minerals
What is the ratio of U-238 to daughter atoms after 5 half-lives?
3.125/96.875
lithification
After the sediment is compacted the dissolved minerals in between the sediment grains crystallize and cement the grains together
Types of unconformities
Angular Disconformity Nonconformity
The geologic history is marked by major changes in
Earth's surface, climate, and types of organisms
Geologic history is separated into
Eons Eras Periods Epochs
two main types of luster
Metallic luster if the mineral reflects light as a polished metal does Nonmetallic luster includes glassy luster, waxy luster, pearly luster, brilliant luster, dull or earthy luster
Naturally occurring
Minerals form and exist in nature Minerals are not manufactured or man-made
Minerals
Naturally occurring inorganic solid specific chemical composition orderly internal structure characteristic set of physical properties
'inorganic'
Not made of living or once living organisms Doesn't contain the element carbon
Life of the Cenozoic era
Oldest to youngest Paleogene Many modern groups of mammals came to be Earliest grasses Neogene Large carnivorous mammals Abundant grazing mammals Quarternary Mammoths, mastadonts Humans
Naturally occurring
Produced through a process found in nature Not man-made; no manufacturing
Orderly internal structure
Regularly repeating crystalline structure
Grades of regional metamorphism
Shale slate schist gneiss
Identify the elements that are in all silicate minerals
Silicone and oxygen
Paleozoic era
Silurian first jawed fish Devonian first insects, seed plants, land vertebrates Mississippian first reptiles Pennsylvanian first winged insects Permian largest mass extinction Invertebrates dominant Early insects, plants, forests
Cenozoic Era
The "age of mammals" Mammals including humans, thrive during this period Divided into 3 periods Paleogene Neogene Quarternary
Consistent chemical composition
The same elements are being used as it grows Whenever you examine the mineral, it has or is the same composition
how do you determine the hardness of an unidentified mineral sample
To determine the hardness of an unknown mineral you would scratch the mineral against those on the Mohs hardness scale. To determine the hardness of an unknown mineral for hardness you must determine the hardest mineral on the scale that the unknown mineral can scratch. If it can scratch a mineral with a hardness of 2 but not a mineral with a hardness of 3 then the unknown mineral has a hardness between 2-3. If two minerals do not scratch each other - they have the same hardness.
Gneiss
a coarse grained rock in which bands rich granular minerals alternate with bands in which schistose minerals predominate
Formation of sedimentary rocks
a cycle weathering erosion deposition compaction lithification weathering...
Law of cross-cutting relationships
a fault or igneous intrusion is younger than any of the bodies of rocks that it cuts through
silicone-oxygen tetrahedron
a four sided structure In silicates each crystalline structure starts with the same building block of 4 oxygen atoms arranged in a pyramid with one silicon atom in the center
Keybed
a layer of sedimentary rock that was laid down over a large area at the same time
Mineral
a naturally occurring, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure and a characteristic set of physical properties
Absolute age
a quantitative (ie - # in years) age determination of a rock or events using radiometric dating
Unconformity
a representation of time when no rock was preserved the rock was either Eroded away or Never deposited in the first place
Felsic
a term derived from the mineral feldspar. Both kinds of feldspar are rich in the minerals silicon (Si) and aluminum (Al).
Foliated
alternating colored bands of different materials
Angular unconformity
an erosional surface between folded and unfolded sedimentary rock
Metallic luster
appears as a polished metal
Sedimentary Rocks
are created by the process of compaction and cementation
Organic sedimentary rocks
are formed from the accumulation of plant and animal remains usually rich in fossils examples of this group of rocks are, coal, which is made from plant remains and fossil limestone, which is made from cemented shell fragments and skeletal remains.
Chemical sedimentary rocks
are formed from the evaporation of seawater or chemical activity also called evaporties The particles or minerals that form these rocks precipitate (settle) to the bottom of the ocean Rock salt is the most common chemical sedimentary rock.
Index fossils
are fossils that are found only in rock layers of a particular age
All sedimentary rocks
are made from sediment
Isotopes
atoms of the same chemical element, each having a different number of neutrons.
3 different textures of sedimentary rocks
clastic crystalline bioclastic
3 types of sedimentary rocks
clastic organic chemical
seven properties that help distinguish one mineral from another
color streak luster cleavage fracture hardness density
After sediment is deposited, more and more sediment is deposited on top of it and this leads to
compaction
Rocks change shape due to three motions
compression tension shear
Increasing grades of metamorphism
crystal size increases
Extrusive
ejected and cooled on the Earth's surface as lava
Once rock is broken down the sediment under goes
erosion
Nonconformity
erosional surface between sedimentary and igneous rocks
Disconformity
erosional surface between unfolded sedimentary layers
Index fossil
evidence of preexisting life that occurs in a rock layer of a particular age
Extrusive
fast cooling lava on the surface small to no crystal fine grained glassy
Metamorphic Rocks
foliated nonfoliated
Metamorphic rocks
form from pre-existing igneous, sedimentary or even other metamorphic rocks through a process called metamorphism
Chemical
formed from minerals that have precipitated out of solution from water
Igneous rocks
formed from the melting and solidification of rock
Organic
formed in layers from the remains of living things
Limestone
forms when microscopic shelled creatures accumulate on the deep ocean floor mostly calcium carbonate shells.
Inorganic substances
not made up of living things or the remains of living things Do not contain the element carbon
Crystal shape
minerals crystals form in one of 6 shapes a certain mineral always has the same general shape because the minerals crystals always combine in the same geometric pattern
Mineral
naturally occurring usually an inorganic substance has a characteristic chemical composition orderly internal substance characteristic set of physical properties
All minerals in nature are/have
naturally occurring inorganic solid a uniform chemical composition an orderly internal structure
abundant grazing mammals
neogene
large carnivores, mammals
neogene
Carbon-14 decays into
nitrogen-14
As you go into the Earth
rocks become progressively older.
Minerals make up rocks
rocks do not make up minerals
Clastic
sedimentary rock formed from pre-existing fragments
Evaporates
sediments made of particles that crystallize as a result of evaporation
Intrusive
slowly cooling, magma underground large crystals coarse grained
Crystals
solids whose atoms and molecules are arranged in a regular repeating pattern
Extrusive rocks
take less time to cool so the crystals grow smaller (ie: fine grained)
Intrusive rocks
take more time to cool, so the crystals grow larger (ie: coarse grained)
Hardness
the ability of a mineral to resist its surfaces from being scratched Doesn't mean "the resistance to being broken" implying that harder minerals are harder to crack
Stress
the amount of per unit created
Uniformitarianism
the assumption that the same natural laws and processes that operate in the universe (including the Earth) have never changed and are the same no matter where you are in the universe
Crystalline solid
the atoms are put together in an orderly way and are grown in that way Can never be a liquid or gas. EVER
Magnetism
the attraction of iron (Fe) containing materials to a minerals surface Usually non-sillicates are magnetic Used to make compasses
Weathering
the breakdown of rock through its exposure air, water, wind, heat, and ice
Regional metamorphism
the changing of rocks due to an increase in heat and pressure in a very large area the degree or the extent of metamorphism depends on the conditions the rock is subjected to
Streak
the color of a mineral in powdered form More reliable than just using the color of the mineral alone
Streak
the color of the mineral in powdered form which you can obtain by rubbing a piece of the mineral against a piece of unglazed ceramic tile
Phosphorescence
the continual glow of a mineral even AFTER the UV light is taken away
Fluorescence
the glow of minerals when under UV light
Lithification
the gluing of sediment grains together to form a rock.
Radioactivity
the increase of energy due to the breakdown of atomic nuclei in the mineral
The longer it takes the rock to cool down
the larger the size of the crystals
Hardness
the measure of the ability of the mineral to resist scratching
The greater the heat and pressure
the more a rock will metamorphose
Metamorphism
the process by which heat, pressure or chemical processes change one type of rock into another.
Density
the ratio of the mass of a substance to the volume of the substance A minerals density depends on the kinds of atoms that the mineral has and how closely the atoms are packed.
Deposition
the setting or precipitation of sediment onto an area
Compaction
the squeezing of sediments together because of all the weight above it
Cleavage
the tendency of a mineral to break along predictable planes (ie - places) of weakness to form smooth, flat surfaces Cleavage planes are parallel to the planes of weakness
Fracture
the tendency of a mineral to break unevenly If the mineral doesn't cleave, it must fracture
Cleavage
the tendency of a mineral to split along specific plains of weakness to form smooth flat surfaces
Erosion
the transport of sediment from one location to another by water, wind, ice, or gravity. Eventually the sediment stops being transported
Sedimentary rocks are formed
through a long process that begins with an already formed rock becoming destroyed The process of destroying a rock is called weathering.
Isotopes
unstable and they decay (half-life)
Schistose foliation
variety of foliation in coarse grained metamorphic rock
Contact metamorphism
when magma touches existing rock, causing it to change. (ie- metamorphose)
Walking the outcrop
when scientists follow a layer of rock from one end of the outcrop to the other
Regional metamorphism
when tectonic plates collide to create tremendous heat and pressure ultimately causing the rock to metamorphose.
If we know the isotopic ratio (remaining parent divided by remaining daughter)
you can use this to determine the age of the rock.
