Earth10 Final UCSC
what determines residence time
large volume and low flux
runoff
movement of water over surface -includes surface flow and streams
elastic deformation
(part of the elastic rebound theory) -rocks deforms like a spring for small differential stresses (elastically) -material changes shape (strain) in response to the stress, but the deformation is not permanent, its RECOVERABLE -> think of silly puddy -if material is above yield strength then stress can cause permanent damage and breaks (ductile deformation or fracture @ brittle deformation)
active margin
- oceanic-continental boundary IS/AT plate boundary -tectonic produces mountainous coastline, +- accretionary prism, uplift, narrow continental shelf. -transform margin is also active margin
ocean waves
-a type of mechanical wave (wave/energy travel thought a medium) are made by winds -are the transmission of energy though water -wind is source but gravity drives propagation -size of wave depends on: 1. wind strnegth 2. wind durartion 3. fetch (distance over which wind pushes
permeability
-ability for fluids to pass through porus material -high porosity doesn't guarantee water flow, rock must also be permeable -ease of flow= hydro logic conductivity
what are the types of glaciers?
-alpine glaciers: found in the mts at high elevation but can flow to lower. local accumulation of snow, sites of accumulation -ice sheets: aka ice caps or continental glaciers. snow accumulation on sheet flows outwards towards margins. position of continents at poles is KEY control on ice sheet accumulation. --> secondary factors: solar influx, atmospheric co2, ocean circulation
sea water composition
-avg salinity is 35g/liter -ions are cl-,Na+, sulfate, so4,mg,ca,k -salinity is not uniformly distributed -->higher salinity at Atlantic bc greater river/continental input -->higher salinity at equator bc enhanced chem weathering input -->lower salinity at N poles bc lower chem weathering input. Sea ice formation excludes salt and drives up local salinity -sequence of salt precipitation from water is dependent upon the relative amount of cations
stream types
-braided: small channels separated by sandbars and islands. -large sediment load and steep gradients. -found near source (ex alluvial fans or near glaciers). -meandering: river with distinct channel that meanders across floodplain. -meanders result in high velocity (site of erosion)and low velocity flow (site of deposition). - both combined lead to migration of meander/river. -bedrock: site of active incision into bedrock. typically associated with tectonically active areas
tides
-caused by gravitational attraction of earth to sun and moon -> as earth rotates, each location will experience max/min of lunar gravitational attraction -controls of tides: 1. rotation of the earth causes 2 high and low tides a day 2. phase of the moon: spring and neap tide 3. shape of the coast line and seafloor: restricted areas will sea large range
why is the sea salty?
-composition controlled by inputs and outputs. -dissolved derive from chem weathering of rocks (easily stripped ions from rocks dissolve easily) -input: weathering of continents (volcanoes, hydro thermal ridges) input from rivers -output: organisms forms shells, bones, and soft parts. (when org dies it sinks to the sea floor, thus removed from the water and can be absorbed by clays and deposited sediments or can evaporate is arid/ isolated regions)
trifecta
-created by 3 dom features 1.active arc 2. Willamette valley 3. coast range
drainage networks
-dendritic (veins that break off) -joint (boxy with joints, ex ucsc) -radical (come off a mountain or volcano) -networks appearance depends on the local geology
elastic rebound theory
-describes how energy accumulates w/in rocks and is suddenly released =>earthquakes -it takes energy TO break rocks -> energy RELEASED is stored w/in rocks as elastic strain which is released upon fault slip --> when rocks break, they DO NOT release energy.
Milankacovitch cycles
-describes the variations in earth's orbit that result in variations in the patter of solar irradiation reaching earth -3 cycles: 1. eccentricity: variations in orbital shape (100,00 yr cycle). very little variation in solar irradiation 2. tilt (obliquity): change in the angle between the earth's axis and the orbital plane (varies between 22- 24.5 deg. 40,000 yr cycle) 3. precession: change in the vector of earths rotational axis (25,000 yr cycle). -the 3 cycles combine to vary pattern of sunlight reaching earth - causes short term cooling of the earth
sea floor
-exhibits varied bathymetry. ->Continental shelf: shallow (0-500m), gently sloping ->continental slope: decends from 500m to 4km ->continental rise: transition zone from 4-4.5 km ->abyssal plain: flat, low relif bottom below 4.5km
surface water
-fresh water -includes rivers, lakes, wetlands -are found within a drainage system or catchment a topo enclosed region with a single surface exit -can lead to erosion of and shaping the appearance of the network -input: precip -output: runoff and evapotranspiration
glacial landforms
-giant glacial lakes form near the ice margin -climate change shows that weather patterns were different and glaciers brought things like rocks to other areas of the country proving there was once an ice age
evidence for last glacial ice age
-glacial deposits -sea level change -isostatic rebound -climate records (O 16, CO2)
what are the controlling factors of rock porosity?
-grain size (big boulders have higher porosity bc lots of space between rocks) -sorting -diagenesis/cement
sea salinity
-high river inputs in Atlantic -high chem weathering input @ equator + high evaporation -sea ice formation excludes salt -highest salinity at surface bc: rivers enter at surface, evaporation at surface, poor vertical mixing -sea salinity is linearly proportionate to density -shallow current = warm, less salty -deep current = cold, high salty
what leads to glacial advance and retreat?
-input of snow > output: --->glacial advance => more snow accumulation converting into ice => time scale dependent ( can occur seasonally of during glacial periods) -input < output: ---> glacial retreat => timescale dependent -ice is always/still moving down gradient
cryosphere
-large water reservoirs -strongly shapes the appearance of our surface bc it's a powerful erosion agent -it leaves behind characteristic land forms => distinct U shaped valleys => glacial till (poorly sorted, high variable grains like silt to boulders =>mirror like surface =>polish is mineralized adhesive that can be dated and record glacial condition (evidence for glaciers)
ice age and glaciation
-last glaciation occurred 20,000 yrs ago -water stored on continental ice shelves instead oceans an => low sea level -ice age controlled by amount of sunlight reaching earth (based on tilt of earth) and amount of co2 in atmosphere
watertable
-line above aquifer. surface marking the upper water saturated zone -if intersects with surface = lake or river -above water table = porus material w/air -can lie in soul but MOST places in w/in sediment or bedrock
what does the central valley consist of?
-marine jurassic cretaceous sedimentary rocks (150-65ma) -cooler climate at this time results in either shallow marine or terrestrial deposits
seismic waves and velocity
-mechanical waves that transfer energy through medium from sources such as earthquakes, explosions, or volcanoes -surface waves travel across the surface and are the slowest. -body waves (p/ primary waves and s/ secondary) travel though the surface and re the fastest -> p waves are compression and go through liquids and solids -> s waves go through liquid ONLY. follows the p wave.
what is the malange (mixture)
-northern coastal ranges which are associated with 80-400 ma subduction -the ranges are a mixture of materials (deep water cherts, pillow basalt, ellogite) scraped off ocean floor
passive margin
-oceanic- continental crust boundary NOT plate boundary -little tectonic activity, often subsiding, wide continental shelf, sediment-rich source to the slope and beyond
California geology
-oldest rocks are 1500-1600 ma in Mojave but most are <500 ma -3 dominate features: 1. Sierra Nevada 2. central Valley 3. coast range
Co2 sinks
-organic material (photosynthesis) absorb carbon and when they are buried it gets absorbed into rocks -silicate weathering (co2 in atmosphere=> acid rain, dissolves silicates) -carbonate shell formations (biological production of carbonates that absorb as limestone)
groundwater overdraft
-overdraft: when groundwater input exceeded by output (both natural or by humans) -results in: lowered water tables, reversal flow, seawater intrusion, subsidence -water removal results in compaction and loss of pore space
snowball earth
-palemoganetic measurements provide the latitude of rock formation. - places of glacial tillites deposited at tropical latitudes -glacial deposits suggest ice moving over carbonate platforms (rocks?) -earth was covered in ice but as volcanoes began to erupt, more co2 was emitted in the atmosphere allowing the earth to warm up
evidence for oxygen in atmosphere
-red beds: sedimentary rocks containing oxidized iron occurred 2.2Ga -irons beds in oceans
carbon reservoirs
-rocks (sedimentary, continental crust) store the most carbon. carbon sequester carbon through burial of organic material -ocean is 2nd largest resv. rock erosion (chemical weathering) and ions get into the water -co2 gets in the atmosphere through volcanoes and humans and life.
water transit: movement between reservoirs/ modes of water travel
-runoff -groundwater flow -atmospheric circulation -ocean currents/circulation -evapotranspiration -evaporation -precipitation
what does the cryosphere influence?
-sea level -ocean circulation -atmospheric and ocean temperatures
evidence for core structure
-since p waves can travel through liquid and solid we were able to measure the waves travel through the core. however s waves travel only though liquid so they could not travel through the solid core, only the liquid mantle and outer core. we were able to figure out the size and where the core was based on where the s waves stopped and bounced back.
groundwater
-subsurface water that occurs below the water table within saturated geologic formations (aka pores are filled) -contrasted with soils that contain air even when wet -source/ recharged by: infiltration/from precipitation (water movement through soil, but not all of that water makes it below the water table) -aquifer: saturated geologic unit that transmits water in large quantities. most are sedimentary rocks but some are igneous or metamorphic (often through fractures)
what are the 2 glacier types?
-temp at base of glaciers controls their rate of movement, ability to erode- 1. Cold base (polar): glaciers are frozen at their base -flow through ice recyrstalization in center -aren't powerful eroding agents of temp glaciers -sharp cliff at glacier snout is key of polar glaciers -glacier flow is ONLY ductile 2. Warm base (temp glaciers): is above freezing point -presence of water lubricates glacial flow -fast moving, powerful eroding agents -glacial flow is BOTH ductile and basal sliding
coastline appearance control factors
-tides: erode -waves and currents: erode -sediment input: creates new coast and shapes appearance -tectonic uplift: strongly controls the appearance if coast line -sea level change: controls location of the coastline and appearance
the hadean: meteorite geochronology
1 my: chondrites and calcium aluminium rich rocks 5 my: eucrites basalts from asteroids dated 5 my after solar system formation 100 my: moon formations, rocks dated to 4.46 -EARTHS OLDEST ROCK: 4.03 Ga -EARTHS OLDEST GRAINS: 4.4 Ga, zircons in ausi -OLDEST LIFE: in Hadean 4.6-4 Ga, more in Archean 4-2.5 Ga
what are the 2 glacial movement/flow responses?
1. Ductile flow: deformation of ice 2. Basal sliding:movement of bed along water-saturated bed of sediment
sediment transport
1. bed load: moves through saltation movement of grain upwards of several cm, following a curved trajectory, back to the bed, striking more grains which then move upwards too 2. suspended load: small solid grains that do not settle (silt size). 3. dissolved load (ions)
what are the 2 kinds of aquifers?
1. confined: groundwater isolated or controlled by an impermeable layers like shale -can provide water to dry regions bc water can move upslope w/in aquifer controlled by the hydraulic gradient and water can be transported away from mt 2. unconfined: aquifers w/ upper surface as water table (upper surface is permeable) -both must be permeable (contain porous rocks
2 variables contribute to non linear density
1. wind and 2. deep currents -polar surface waters are generally denser bc wind pushed equatorial salinity surface water to polar region -->water cools and increases density and sinks-> deep currents are thus cold and only return to surface via warming or mixing with low salty water -equatorial surface waters are generally low density
O 16 and O 18 reservoirs and its relation to past climate-oxygen measurments
O 16 and O 18 are both found in the ocean how during evaporation O 16 is evaporated because it is lighter. when it snows, O 16 is released and can accumulates in air pockets/ bubbles as glaciers form and the snow compacts. when researching later about the climate, we can drill into glaciers and see what how much O 16 is stored and it contains to find out more about the climate during that time. meanwhile O 18 accumulates in the ocean. -if there is no glacier formations then O 16 goes back into the ocean
attrition
breaking of existing fragments through impacts of one anothr and bed
knickpoint
change, typically sharp, channel slop reflecting rapid changes to landscape -sources are faults, lava flows, damns, drop in baselevel -often result in water falls -change the equilibrium profiles bc migrate backwards, erosion propagating towards headwaters to return river back to equilibrium
evapotranspiration
combination if evaporation and transpiration (release of water from plant leaves)
ocean currents/circulation
combination of surface currents driven by wind that moves near surface warm water and the sinking of cold water at the polar regions that drives deep circulation return -wind drives shallow water ocean currents -thermal and salinity differences drives deeps water currents
precipitation
condensation of atmospheric water that upon gas change and falls because of gravity as rain or snow
sediment budget
controls appearance of coastline by: -inputs (rivers and erosion by wave and wind) -transports (by near shore currents; mainly long shore drift from N to S. <long island ex>) -output (deposition up beach on dunes, deeper water)
MOHO
crust- mantle boundary -> is seismically detected by a dramatic increase in seismic velocities
dissolution
dissolving soluble material
Earthquakes
energy is released at earthquakes. -energy propagates AWAY from energy source (bc elastic rebound theory)
why do swells arrive in sets
fastest moving waves have the longest wave length bc they run into and constructively interfere with other waves making bigger waves
what drives glacial flow?
glaciers flow bc gravity steps for glacial flow: 1. snow accumulates in "zone of accumulation (varies through geo location on earth) 2. snow recrystallizes into ice due to compaction 3. glacier flows sown gradient (from thick to thin ice) 4. ice volume is lost in "zone of ablation" -equilibrium line (ELA): position of equilibrium ice accumulation and ablation. It's higher at lower altitudes and shifts to lower elevations during last ice age
stream features
headwaters = source -mouth: located at the baselevel which can no longer be eroded, sediment it dropped off -baselevel: often is lake or sea level -channels: confine of river in which water flows -equilibrium profile: stable level of erosion and deposition. all rivers evolve towards this -floodplain: area next to channel, over which flooded water may flow and deposit material.
Permian extinction 298.9-252.17
high co2 causes ocean acidification and animals die
evaporation
liquid to gas conversion from bodies of water such as the ocean and lakes
abrasion
particles suspended by river scour the river bed
seismic waves and reflection and refraction
reflection: reflects upward from encountering boundary refraction: bending of ray path when encountering material (downwards) seismic waves will reflect and refract when they encounter a boundary like the core. -waves travel faster in cooler and harder rocks
hydraulic action
removal of rock fragments from force of water on bed
how does snow turn into ice?
snow accumulates and compacts with time
hydrologic cycle
storage of water in reservoirs and the movement between them -not all reservoirs hold the same amount of water, and have different residence times ->oceans is largest reservoir, atmosphere is smallest
stress v strain
stress: measure of the internal forces that neighboring particles of material exert on one another -> faults (stress): faults applying stress on another strain: is the measure of how a material deforms in response to stress
how has climate changed over the past 65ma?
the climate has gotten cooler, currently we are in an ice age (interglacial) data indicates that the oceans are enriched in O 18 and O 16 is stored in ice
sea surface temp
thermal gradient driven by convection in oceans because different regions of earth had more or less sun exposure
atmospheric circulation
thermally driven convection of air -water as vapor/gas is part of atmosphere (not just in clouds). smallest reservoir and shortest residence time. -this is how water is rapidly moved around the earth -wind drives shallow water ocean currents -wind works to create an equilibrium temp
groundwater flow
water that has infiltrated the ground at a "source" or "recharge" region and flows through the soil, rocks, or cracks/faultsat in rocks on variable timescales (years, centuries, millennia).
why do waves break?
when waves approach shores they: -"feel bottom" = rotating water touches the bottom -touching the shores force the water to life and steepen peak -vaves break when water depth is 3/4 of wave height