Earth Science Flashcards
What is geology?
the science that deals with the earth’s physical structure and substance, its history, and the processes that act on it.
These rocks are formed when magma (molten rock) from the Earth’s interior cools and solidifies.
igneous rock
A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.
Metamorphic rock
A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together
Sedimentary rock
Rock that forms when magma cools above the surface of the Earth
They cool quickly and are fine-grained or lack crystal growth.
Extrusive igneous rock
igneous rock that formed below Earth’s surface.
They cool slowly and as a result form visible crystals (coarse-grained.)
intrusive Igneous rock
The process that converts sediments into solid rock by compaction or cementation.
Lithification
What are the two main branches of geology?
physical and historical
What is historical geology?
study of the physical processes and changes of the Earth through time.
Changes = Evolution
Studies the origin and evolution of the earth, its continents, oceans, atmosphere, and LIFE
Volcanic Activity -> Weathering -> Transport (Erosion) -> Deposition -> Metamorphism -> Melting -> Magma
Rock Cycle
Dentrital and Chemical
Methods of Classification
foliated and non-foliated
Metamorphic rock classification
Constructive = Building
Destructive = Erosive
Two main geological processes
a coherent explanation for one or several related natural phenomena supported by a large body of objective evidence.
In other words, it is a hypothesis that has been tested many times and nothing has disproved it. Explains why
Theory
965 -1040 AD
Born in Iraq, lived in Egypt & Spain most of his life.
Scientist:
Optics, Physics, Astronomy, and Mathematics
Called by many the father of the scientific method
Alhazen
a method of procedure that has characterized natural science since the 17th century, consisting of systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.
What is the scientific method?
Define a question -> Background research -> Hypothesis -> Test Hypothesis -> Analyze Data -> Interpret Data -> Conclusions -> Publish -> Retest
The Scientific Method
generalizes a body of observations, nothing has disproved it yet- doesn’t explain why
Law
does not imply causation
Correlation
complex, conscious thought
What distinguishes humans from all other species?
What is the universe defined by astronomers?
All of the space and matter and energy within
The theory is that the universe originated in a huge explosion that released all matter and energy.
Big Bang Theory
What is cosmology?
The scientific study of the universe
The universe is expanding and background radiation
Evidence for the Big Bang
1929
Velocity increases proportionally
Spectral Lines
Doppler Effect
Edwin Hubble (1889-1953)
high frequency, short wavelength (compressed)
Blue light
low frequency, long wavelength (spread out)
Red light
What happened after the Big bang (Step 1)?
Basic forces emerged such as gravity, electromagnetism, and strong & weak nuclear.
What happened after the Big bang (Step 2)?
100% Hydrogen (H) and Helium (He) –> 98% Hydrogen (H) and Helium (He) & 2% all other elements
part of the milky way galaxy
Solar nebula theory
Our solar system
How are heavier elements formed?
Stelluar nucleosynthesis and elements formed past Iron (Fe) are formed in a supernova.
The ball at the center grows dense and hot –> Fusion reactions begin, the sun is born –> Dust in the rings condenses into particles –> Particles coalesce to form planetesimals.
Formation of the Solar System
Anything that has mass and takes up space
What is matter?
A substance that cannot be broken down into simpler substances
What is an element?
The basic unit of matter; structure, atomic number, and atomic mass, made of protons and neutrons and surrounded by electrons with a nucleus in the center.
What is an atom?
Atoms of the same element that have different numbers of neutrons
Isotopes
electrons in the outermost shell
valence electrons
2 or more elements chemically combined
Compounds
A group of atoms bonded together
Molecule
Ionic = Transfer
Covalent = Share
Chemical bonds
unequal sharing of electrons
Polar Covalent
Why is Polar Covalent important in nature?
Water
a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition
What is a mineral?
minerals that contain silicon and oxygen and usually one or more other elements.
Ex: Quartz, feldpars, (orthoclase and plagioclase), olivine, pyroxenes, amphiboles, and biotite.
Silicates (SiO2)
No Si (Silicon) and O (Oxygen)
Ex: Carbonates, Halidies, Native Elements, Oxides, Sulfates, and Sulfides.
Non-silicates
The arrangement of atoms and shapes varies based on bonds.
Crystalline structures
silicon-oxygen tetrahedron
Silicate Structures
form rings by sharing oxygen atoms
ring silicates
form a chain by sharing oxygen atoms
single chain silicates
form when two single chains of tetrahedra link to each other by sharing oxygen atoms
double chain silicates
Varying chemistry - many crystal forms
Cubes, hexagons, etc
Tetrahedrons are possible but not around Si (Silicon)
Properties determined by crystal pattern - native elements have closely spaced atoms = high density
Non-silicate structures
Study of Earth time
Geochronology
the branch of geology concerned with the order and relative position of strata and their relationship to the geological time scale. (Putting Geological events in order)
Stratigraphy
The study of the vertical layering of rock types. (Using rocks)
Lithostratigraphy
a relative dating technique based on the regular changes seen in evolving groups of animals as well as the presence or absence of particular species. (using fossils)
Biostratigraphy
absolute ages of rocks, as agreed upon by an international team of geologists (Using radioactive dates)
Chronostratigraphy
Determines how old something is in relation to something else.
(Not a number).
Ex: I am older than my brother but younger than my father
relative age dating
superposition, original horizontality, lateral continuity
Steno’s laws
the principle that in undisturbed rock layers, the oldest rocks are on the bottom
Superposition
layers of sediment initially extend laterally in all directions
Lateral Continuity
The principle states that sedimentary rocks are deposited in horizontal or nearly horizontal layers.
original horizontality
Younger layer slices through the older surrounding layers (Fault line, Magma, etc).
Cross-Cutting (Hutton)
a piece of older rock that becomes part of a new rock
Inclusion
Fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.
fossil succession
an unconformity in which younger sediment or sedimentary rocks rest on the eroded surface of tilted or folded older rocks
angular unconformity
A gap in sedimentary rock record due to subaerial exposure.
Disconformity
Sedimentary rocks sit on metamorphic or igneous rocks.
Non-conformity
units in unbroken vertical succession record environments that would have been laterally adjacent
- implies TIME TRANSGRESSION during depositional events
Walther’s Law
a method that enables scientists to determine the actual age of certain rocks and other objects
Ex: Dendrochronology, Ice core measurements, written accounts/records.
absolute age dating
The process of counting tree rings to determine the age of a tree
Dendrochronology
A spontaneous process in which unstable nuclei lose energy by emitting radiation. Alpha Decay, Electron Capture; Have loss of subatomic particles leading to a change in the structure and potential charge.
radioactive decay
Determining the age of a rock or mineral through its radioactive elements and decay products.
isotope dating
The time it takes for half of an isotope to decay
half-life
What percent of Carbon-14 would you expect from a sample from 11,000-12,000 years ago?
Reference: Half-life for Carbon-14 is 5,730
25%
A sample shows 35% Carbon-14 at 20,000 years is this correct?
Reference: A Half-life for Carbon-14 is 5,730 years
No, it is not correct because 50% and 25% of the parent material in Carbon-14 ranges from 5,730 years to 11,460 years.
isotope age dating lab conditions:
Assumes closed system
No one leaks out
No one leaks in
All products produced by decay
Clean lab conditions
Cost and Economic pressures
Not a new idea.
Continental fit
Plant fossils
Glaciations
Seuss
Continental movements
Mountains = lateral movements
Taylor
German Meteorologist & polar explorer
Continental drift
Pangea
Tons of Data!
Alfred Wegener
Wegener supporter
Further developed continental drift hypothesis
Climate paradox
Laurasia
Alexander Du Toit
Evidence of Late Paleozoic glaciers found on five continents.
Some of this evidence is now far from the poles.
These glaciers could not be explained unless the continents had moved.
Glacial Evidence
Placing Pangaea over the Late Paleozoic South Pole:
Wegener predicted rocks defining Pangea climate belts.
Tropical coals
Tropical reefs
Subtropical deserts
Subtropical evaporites
Paleoclimatic evidence
identical fossils found on widely separated land masses.
Mesosaurus– A freshwater reptile
Glossopteris– A subpolar plant with heavy seeds
Lystrosaurus– A nonswimming, land-dwelling reptile.
Cynognathus- A nonswimming, land-dwelling mammal-like reptile.
Fossil Evidence
A physical phenomenon resulting from the spin of electrons in some solids–particularly those of iron– and moving electricity
Magnetism
An area in which magnetic substances such as iron are affected by lines of magnetic force emanating from the earth.
Magnetic field
difference between geographic north and magnetic north.
Depends on:
The absolute position of the two poles and longitude
Declination
The angle between the magnetic field line and the surface of the earth.
Depends on:
Latitude
Inclination
the study of fossil magnetism
Paleomagnetism
-high temp-no magnetization
-thermal energy of atoms is very high
-magnetic dipoles are randomly oriented
hot magma
- Low Temp: permanent magnetization
- Thermal energy of atoms slows
- Dipoles align with Earth’s magnetic field
- Magnetic dipoles become frozen in alignment with the field
cooled magma
Before World War II, little was known about the sea floor
*Echo-sounding (sonar) allowed rapid sea-floor mapping
-Sea-floor maps created by ships crossing the oceans.
-Bathymetric maps are now produced using satellite data.
Sea Floor Bathymetry
The oceanic crust is covered by sediment-
Thickest near the continents-
Thinnest (or absent) at the mid-ocean ridge
The oceanic crust consists primarily of basalt-
Lacks a variety of continental rock types
Heat flow is much greater at the mid-ocean ridges.
The Oceanic Crust
The process by which molten material adds new oceanic crust to the ocean floor; Old ocean floor sinks into the mantle and magnetism in sea floor rocks varied farther from MOR
sea-floor spreading
Changes in Earth’s magnetic field over geologic time, recorded in ocean-floor rocks and continental basalt flows- Reversals occur at uneven intervals- Longer intervals (500 to 700+ Ka) are called chrons- Shorter intervals (~200 Ka) are subchrons
Magnetic reversals
It provides a unified mechanism explaining:
◦The distribution of earthquakes and volcanoes.
◦Changes in past positions of continents and ocean basins.
◦The origins of mountain belts and seamount chains.
A unifying theory
A theory stating that the earth’s surface is broken into plates that move - the earth’s outer shell is broken into a rigid plate that moves.
Plate motion defines three types of plate boundaries.
Plate Tectonics
A rigid layer made up of the uppermost part of the mantle and the crust. Continental - 150km thick, Oceanic - 100km
in motion over the asthenosphere
Bends elastically when loaded
Asthenosphere flows plastically when loaded
Lithosphere
Where land meets the ocean
continental margin
Tectonic plates move apart.
Forming either rift valleys or mid-ocean ridges (MOR)
divergent boundary
Tectonic plates move together
Causes uplift or subduction
convergent boundary
Tectonic plates slide sideways.
Transform boundary
Magma from deep within the mantle melts through the crust above it.
Hot spots
The driving mechanism of plate tectonics
Convection
Ridge-push
Slab-pull
An episode of intense rock deformation, or mountain building, results in compressive forces generated by collision.
Orogeny
The relationship between mountain building and the opening/closing of ocean basins.
Wilson Cycles
Importance of sedimentary rocks
preserve evidence of surface processes responsible for deposition, many contain fossils that are rare or absent in most other rocks, and many are resources or host rocks.
Sedimentary rocks form at or near Earth’s surface in one of several ways:
Cementing loose clasts (fragments) of preexisting rock.
Cementing together loose shells and shell fragments.
Accumulation of organic matter from living organisms.
Precipitation of minerals dissolved in water.
Clastic: Loose rock fragments (clasts) cemented together.
Organic: Carbon-rich remains of once-living organisms.
Biochemical: Cemented shells of organisms.
Chemical: Minerals that crystalize directly from the water.
Geologists define four classes of sedimentary rocks
Classified on the basis of texture and composition:
Clast (grain) size
Clast composition
Angularity & Sphericity
Sorting
Character of cement
the degree of edge or corner smoothness
Negligible transport (younger)
angularity
the degree to which a clast nears a sphere
Long transport distances (Older)
Sphericity
the uniformity of grain size
Sorting
all clasts have nearly the same grain size
Well-sorted
clasts show a wide variety of grain sizes
poorly sorted
features that developed during or shortly after the deposition of the sediments
sedimentary structures
Sedimentary rocks are usually layered or stratified.
Arranged in planar, close-to-horizontal beds.
The boundary between two beds is a bedding plane.
Several beds together constitute strata.
Bedding and stratification
Why does bedding form?
Bedding reflects changing conditions during deposition.
Bedding forms due to changes in:
Climate
Water Depth
Current Velocity
Sediment Source
Sediment Supply
bedding or stratification
A sequence of beds
Water or wind flowing over sediment creates
bedforms
Bedform character is tied to
Flow velocity
Grain size
cm-scale ridges and troughs.
Develop perpendicular to flow
Frequently preserved in sandy sediments
Found on modern beaches
Found on bedding surfaces of ancient sedimentary rocks
ripple marks
similar to ripples except for much larger
Form from water or wind-transported sand.
Occur in streams and in desert or beach regions.
Range in size from tens of cm to hundreds of m
Often preserve internal cross beds.
Dunes
created by ripple and dune migration; sediment moves up the gentle side of a ripple or dune; sediment piles up, then slips down the steep face
Cross beds
Sediment moves on a slope as a pulse of turbid water.
As pulse wanes, water loses velocity and grains settle.
Coarsest material settles first, medium next, then fines.
This process forms graded beds in turbidite deposits
Turbidity currents and graded beds
occur after deposition while sediment is still soft
Bed surface markings
polygonal desiccation features in wet mud, indicate alternating wet and dry terrestrial conditions
Mudcracks
troughs eroded in soft mud by current flow
Scour marks
evidence of past life
footprints
Shell impressions
Fossils
Locations where sediment accumulates. They differ in:
Chemical, physical, and biological characteristics. Sediment delivery, transport, and depositional conditions. Energy regime.
Environments include Terrestrial,Coastal, and Marine.
depositional environment
large areas where sediment accumulates.
Thin to absent where nonsedimentary rocks outcrop
thicken to 10-20 km in sedimentary basins
Sedimentary basins
sinking of the land during sedimentation
Subsidence
Craton side of the collisional mountain belt
The weight of the mountain belt pushes down the crust’s surface
Foreland basin
Divergent (pull-apart) plate boundaries.
downward slip on faults produces narrow troughs
Rift basin
Interiors far from margins.
the basin forms in the interior of a continent, perhaps over an old rift
intracontinental basins
Continental edge is far from the plate boundary.
subsidence occurs over thinned crust at the edge of an ocean basin
passive margin basin
flooding due to sea-level rise.
Sediment belts shift landward; strata “deepen” upward.
transgression
Exposure due to sea level fall
Regression
Physical, chemical, and biological changes to sediment.
Lithification is an example of it.
As sediments are buried, pressure and temperature rise.
Diagenesis
