physical geology
-the science of earth
-reshapes Earth's interior, sculpts Earth's surface, determines the distribution of metals and petroleum, controls which places are most susceptible to volcanoes/floods/natural disasters, explains how different features came to be
-t
atmosphere
-component of the Earth System
-air
hydrosphere
-component of the Earth System
-water and ice
biosphere
-component of the Earth System
-plants and animals
geosphere
-component of the Earth System
-land, rocks, solid earth
science
-a process of discovery that increases our body of knowledge
-information that can be learned, is waiting to be discovered, and shared
-curiosity and creativity in the search for answers to questions
hypothesis
-a testable explanation/interpretation that can be verified or falsified
-based on data and interpretations combined to form a possible explanation
-an explanation developed to explain observations and allow testing
-if true, you can predict what will hap
prediction
-a statement of what will happen in a given set of circumstances or situation
scientific process
-observe, question, interpret based on analysis of date, form a testable hypothesis, make predictions, preform tests, analyze results, make a conclusion
-consider different types of data and different scales of observation
-test alternate explanations!
observations
-facts, measurements, data collected by using the senses
-valid _____ become data that can be used to develop possible explanations
-evaluating the validity of _____ is critical, so geologists commonly repeat measurements to compare values
shoreline
-boundary between continent and ocean
continental shelf
-shallow seafloor, considered part of the continent (edges)
-smooth vs. rough deep parts of the ocean
shaded relief map
-emphasizes shape by simulating light and dark shading
-represents features on land surfaces (shape, but not specific geology)
topographic map
-shows the elevation of the land surface with a series of lines called contours
-widely spaced contours = flat land; closely spaced contours = steep land
-represents features on land surfaces (shape, but not specific geology)
index contours
-darker every 5th contour on a top0graphic map to emphasize broader patterns
satellite image
-computer processed image showing the distribution of different types of plants/rocks/etc.
-depicts the types of materials on Earth's surface
geologic map
-represents distribution of rock units and geologic features on the surface of Earth
-most important/useful
-shows age and type of rock/sediment as well as geologic features
quantitative
-data
-numeric, typically visualized/analyzed using data tables/calculations/equations/graphs
-measurements, numbers, result from scientific instruments or simple measuring devices
qualitative
-data
-simple descriptions, descriptive words, labels, sketches, and other images
-ex. color, texture, density, size, location, etc.
orientation
-quantitative property measured in the field
-layers, fractures, folds, tilts
surface features
-quantitative property measured in the field
-mark locations of data and movement of the land surface before/after an earthquake or volcanic eruption
gas composition
-quantitative property measured in the field
-quality and composition of volcanic gases as they change over time; valuable clues for whether a volcano is preparing to erupt
water flow and chemistry
-quantitative property measured in the field
-measure the velocity and volume of flowing water
-chemical analysis to document what the water contains
physical properties
-quantitative property measured in the lab (requires lab environment for prep of samples and analysis with sophisticated scientific instruments; main source of understanding)
-density, strength, etc. to evaluate how rocks behave when subjected to forces
composition
-quantitative property measured in the lab (requires lab environment for prep of samples and analysis with sophisticated scientific instruments; main source of understanding)
-chemical analysis and percentage of different materials provide info about ____
age
-quantitative property measured in the lab (requires lab environment for prep of samples and analysis with sophisticated scientific instruments; main source of understanding)
-measure the ratios between different types of radioactive elements
density
-controls regional elevations and causes forces that result in earthquakes
-determined by directly measuring a rock, the pull of gravity, of by numerically analyzing how fast seismic waves pass through materials between an earthquake and a seismic recordi
weight
-downward force exerted under the pull of gravity
-depends on how much mass and strength of gravitational field
data
-qualitative or quantitative
-useless without context
interpretation
-analysis of data
-several _____s fit together to make a coherent story
-combine with data to from a hypothesis
hot spot
-melting of rocks at depth resulting in volcanism on the surface
-most likely to be found in interiors of plates
-melting by decompression
theory
-widely accepted and supported by a rigorous body of knowledge
-examined and tested many times
-a hypothesis that survives scientific scrutiny and is lifted to a higher standard of credibility
-encompasses an extensive body of knowledge
-CAN CHANGE OVER T
geologists investigate questions with...
-field studies
-labs
-outdoor experimental facilities
-numerical modeling
(common goal is to understand the area's geologic processes and history)
geologists study inaccessible places with...
-telescopes
-hi res imaging devices
-scientific instruments
-remote probes and satellites
Walter and Luis Alvarez
-scientists who proposed the hypothesis that dinosaurs were wiped out by the impact of an asteroid/comet with the Earth
crust
-outermost layer of Earth
-includes continental and oceanic _____s
-thickness controls regional elevation; thin = low elevation / thick = high elevation
continental crust
-thin
-low density
-granite like composition
oceanic crust
-beneath deep oceans
-very thin (thinner than continental crust)
-high density (denser than continental crust, but less dense than mantle to rest on it)
-basalt like composition
mantle
-middle layer of Earth
-mostly solid
-upper part is plastic, slowly flowing asthenosphere (upper 10%)
-lower 90% is not involved with plate tectonics, contains minerals formed at high pressures
core
-deepest layer of Earth
-dense, metallic; formed as iron sank to the center driven by gravity
-consists of metallic iron and nickel
-divided into two parts: outer molten ___ and inner solid _____
lithosphere
-composed of the crust and upper mantle (_____-ic mantle)
-strong and solidly attached
-thickness controlled by temperature; expands in heat, becomes less dense, rises in elevation
-broken into rigid pieces called tectonic plates
asthenosphere
-mantle below the lithosphere
-mostly solid but can flow slowly under pressure
-functions as a soft, weak zone for lithosphere to move over
-hotter
seamounts
-mountains on the seafloor below sea-level
-formed by series of volcanic eruptions, usually associated with a hot spot
1. magmatism starts building a submarine volcano by eruption of lava onto seafloor
2. continued eruptions build up volcano until it rise
abyssal plains
-smooth and deep ocean floor
-most of ocean floor
-gentle slope
-4.5 k below sea level
-smoothed by sediment
-contains isolated seamounts
-cooler, more dense, lower elevation than ocean ridges (subsidation slows/stops when oceanic crust reaches equilibriu
mid-ocean ridges
-broad symmetrical ridges across ocean basins, higher than seafloor
-underwater mountain ranges
-tectonic plates often diverge here; represent most plate boundaries
-found is all ocean basins
-sites of many small to moderately sized earthquakes and much s
oceanic fracture zones
-cracks and steps across the seafloor mostly at right angles to mid-ocean ridges
plateaus
-broad high regions (both continental and oceanic)
oceanic:
-largely composed of flood basalts
1. formed at hot spots above rising mantle plumes (travel through mantle as solid masses)
2. causes widespread lithosphere melting; submarine flood basalts pour
ocean trenches
-deepest parts of the ocean
-mostly the Pacific
-often along edges of the ocean and continents
-represent most plate boundaries, particularly convergent boundaries
-generate the largest volcanoes above
island arcs
-curving chains of islands, mostly active volcanoes
-most flanked by an ocean trench at the edges of oceans
-ocean/ocean boundary: melting by addition of water to upper mantle (same applies to volcanic arcs at ocean/continent boundary)
continental drift
-proposed by Alfred Wegener
-argued that continents were once together but later drifted apart
-alternate to land bridge theory
-continents seemed to fit together like puzzle pieces
-corresponding edges of different continents have similar rocks and geolo
land bridge
-a possible explanation to the linking characteristics of Africa and South America
-if these existed, then the South Atlantic Ocean should contain (remnants of) submerged ridges that once connected the two continents
-has been falsified
internal heat
-rises and causes plate tectonics
-interior of Earth is losing heat from the formation process (Earth formed from accumulation of dust/gas and collisions of smaller planetary bodies; collisions caused heat)
-mostly generated by radioactive decay of elemen
convection
-cyclical flow of heat
-magma rises from the center to disrupt and move plates (both continental and oceanic)
-multiple magma points coming come up very slowly through the mantle and spread out while cool material sinks back in
-loss of heat from Earth's
tectonic plate
-composed of the continental and ocean crusts + the upppermost mantle (lithospheric mantle) = rigid and mobile lithosphere
-moves over the asthenosphere (hot and weak, mostly solid/plastic, slowly flows)
-90% of mantle is not involved
-they move 1-15 cm/y
linear island chain
-located in the middle of oceans
-different in character and origin from island arcs (which are related to subduction)
-most are in Pacific Ocean
-usually have an active volcano; land is younger there and progressively ages as you move farther away
-forme
earthquakes
-distributed in lines, mostly on mid-ocean ridges, island arcs / volcanoes, trenches, and major mountain belts
-a better guide to plate boundaries than volcanoes
-sometimes occur in the middle of plates, indicating a weak point and potential rift
-associa
volcanoes
-located relative to linear chains of oceanic islands, mountain belts next to trenches, island arcs next to trenches, and the Red Sea / East Africa rift
-widespread along mid-ocean ridges, but generally does not form mountains
-generally indicate trenches
tectonic activity
-also known as the theory of plate tectonics
-moves in belts
-processes that deform the crust and mantle
-stable regions with active edges
-regions between the belts are relatively stable
-outlines the shapes of the plates
-circulates material between the
divergent boundary
-plates move apart from each other, commonly filled with magma
-one continents, can split a continent and form a new ocean basis as the pieces move apart
-new oceanic lithosphere formed as oceanic plates spread apart
-boundaries called spreading centers
-
convergent boundary
-plate move toward one another, commonly resulting in one plate sliding underneath the other
-typically characterized by ocean trenches
-oceanic trenches, island arcs, and the largest mountain belts form here
-many of the most dangerous volcanoes and eart
transform boundary
-two plates move horizontally past one another
-plates slip horizontally past each other along transform faults associated with mid-ocean ridges
-combine with spreading centers to form zigzags on the seafloor
-transform faults can link different types of
spreading centers
-an area in a divergent boundary where plates move apart due to the uplift of hot melted mantle from the asthenosphere
-youngest ocean crust is found here
Seafloor Age
-crust should be youngest near the ridge's spreading point and progressively older away
rift
-axis of most mid-ocean ridges
-forms as large blocks of crust slip down during spreading
-movement causing faulting which leads to frequent small earthquakes
continental rifting
-type of divergent boundary motion
-can lead to seafloor spreading and formation of a new ocean basin
1. broad uplift of land surface as mantle-derived magma pushes up the crust
-magma heats/melts parts of the continental crust, making more magma; heating
passive margin
-a continental edge that lacks activity
-formed by a continental rift due to divergent boundary activity
ocean-ocean convergent boundary
-where two oceanic plates converge
1. two oceanic plates converge together; one plate is forced underneath the other in the process of subduction (greater density plate will subduct. greater density plate will be older / cooler / have accumulated more sed
subduction
-process of one plate sliding beneath another plate
-at a convergent boundary, the mantle in the over-riding plate is melted to from magma, NOT melting the subducting plate; slab releases water at high pressure, squeezing water our of minerals -> WATER ca
subduction zone
-the zone around a downward moving plate
-many large earthquakes occur here
accretionary prism
-a wedge beneath an oceanic trench that collects sediment and crust slices
ocean-continent convergent boundary
1. oceanic plate and continental plate converge; the denser oceanic plate subducts beneath the more buoyant continental plate; oceanic plate always subducts and is destroyed
2. oceanic trench marks plate boundary, receives sediment from adjacent continent
Pacific Ring of Fire
-volcanoes surround the Pacific Ocean
-results from subduction on both sides of the ocean
1. new oceanic lithosphere forms along a mid-ocean ridge, then moves away as seafloor spreading continues
2. oceanic lithosphere subducts neath the continents on bot
continent-continent convergent boundary
-often called a continental collision
-produces huge mountain ranges
-preceded by subduction of oceanic lithosphere that brings continents closer
-produces the thickest continental crust and tallest mountains (70km high vs. average 35-40km thick continent
transform faults
-diverging plates pull apart, breaking at the weakest points (creates a zigzag pattern); new oceanic crust forms in the breaks
-spreading zones are linked by breaks or faults, where the two plates simply slide by each other (no gaps, only horizontal movem
driving force
-a force that drives motion
-must exceed RESISTING FORCES (friction, other resistance)
slab pull
-gravity pulls dense subducting oceanic lithosphere faster than non-subducting plates
-sets up other forces in the mantle that can work with or against
ridge push
-gravity causes ridge plates to slide down and push the plate out
mantle convection
-hot materials rise, cool, and eventually sink back into the asthenosphere
-occurs at mid-ocean ridges and hotspots (centers of upwelling mantle material, usually in the interior of plates)
Edward Bullard
-scientist who showed the continents fit together better when you include the continental shelves
-previously joined continents should have common geological features (same age/type of rocks/fossils)
pillow basalt
-basaltic lava that erupts within a rift as the oceanic crust stretches apart
dikes
-solidifies magma-filled fissures
carbonate compensation depth
-the depth at which calcite disappears (carbonate minerals dissolve into seawater as fast as they accumulate at 4,500/5,000m depth and greater)
fast spreading ridge
-broad, no large well-developed rift in center
-allows new oceanic crust to move far from the spreading center before it cools and subsides
-interpreted to have more underlying magma (rapidly pours our of fissures onto surface rather than forming a large
slow spreading ridge
-allows rocks near the ridge to cool and strengthen enough to form large faults
((the mid-ocean ridge in the Pacific is spreading faster than the Atlantic, so it's broader and lacks a well-developed rift))
black smokers
-hydrothermal vents
-hot water jets out and cools, dissolved elements form small crystals that make the water black and cloudy
chimney - hollow circular column formed by sulfur bearing minerals around the vent; interpreted to have formed on mid-ocean ridg
continental margin
-thickest sediment is found along here, especially those formed by rifting; also thickest near river mouths where oceanic crust is relatively old
-major rivers deposit large volumes of sediment as water reaches the river mouth
continental interior
-relatively tectonically stable
-can be affected by tectonic events along distant plate boundaries
-strongly influenced by global environmental fluctuations (climate and sea level -> climate change /due to global or regional effects/ can affect sea levels
continental shield
-central region of older crystalline (metamorphic and igneous) rocks
-exposed rocks represent the kinds of rocks that underlie much of the continent (crystalline basement)
crystalline basement
-exposed rocks in the continental shield represent the kinds of rocks that underlie much of the continent
-large stresses from plate boundaries/distant mountains may cause movement on ancient faults here, forming folds/faults/domes/regional basins
continental platform
-surrounds the shield
-characterized by nearly horizontal rocks that were deposited on top of the basement (layers commonly contain broad basins and uplifts)
unconformity
-boundary between flat-lying platform sedimentary rocks and underlying crystalline basement
-separates rocks with very different ages/structural geometries/geologic histories
tectonic terranes
-pieces of crust embedded within continents that have a different geologic history than adjacent regions
-bounded by faults (no continuous link with the rocks around it)
-has different sequences and ages of rocks than adjacent regions
-different fossils,
origin of magma
Magma is generated in the shallow part of the mantle under conditions where we add water or there is a significant decrease in pressure (such as under an oceanic ridge). The magma under the oceanic ridges that forms new oceanic crust does come from the as