question

the most common type at earth's surface what do we use sedimentary rocks for --1.) construction sites and building materials --2.) almost all fossils are found in sedimentary rocks --3.) fossil fuels --4.) soils --5.) landslides

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Sedimentary Processes

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the original rock from which something else was found does not matter what type of rock

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Parent rock

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breakdown of rock into particles

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weathering

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mechanically or physically break the rock down --ex: roll it down a hill to make it break apart

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physical weathering

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rocks easily break apart

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natural zones of weakness exist in some rocks

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plant roots can force their way through solid rock splitting the rock apart --ex: root cracks in sidewalks

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biological activity

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-when water freezes it expands so the ice presses against the sides of the crack making it wider -each time water gets in the crack and freezes the crack widens until it finally splits --ex: pot holes

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Frost wedging

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-more common in many environments -diff minerals will react at diff rates -last minerals to form in Bowes reaction series are the more stable at earths surface -first minerals to form in Bowes reaction series are the least stable at earths surface --dissolve it in acid ---feldspar +H2O + H2CO3 => kaolinite + dissolved ions

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chemical weathering

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soft, thoroughly decomposed and porous rock, often rich in clay. Generic rock that has all minerals weathered away -common in SC in the layers of the earth

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Saprolite formation

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when oxygen combines with other elements in rocks to form new types of rock. These new substances are usually much softer, and thus easier for other forces to break apart

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oxidation

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moving sediment from one place to another 4 things in nature commonly cause erosion -1. water -2. wind -3. gravity (landslides) -4. ice (glaciers)

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Erosion

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any natural depression that can hold sediment

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basin

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the amount of space available in a basin to hold sediment

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accommodation space

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as sediment is deported its weight may cause the basin to sink

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subsidence

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layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers

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strata aka beds

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process of becoming solid rock

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lithification

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-compaction -cementation

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lithification steps

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pack the layers of sediment together. can do this by adding layers to the basin in order to create more pressure on the particles to get closer together

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compaction

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stuck together with natural cements -water is squeezed out dissolved materials in the water get left behind

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cementation

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*classified by grain size -produced by physical weathering

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Clastic (detrital) sediments

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how uniform are the grains in a rock. -well sorted --grains are very similar in size -moderately sorted --grain sizes mixed together -poorly sorted --lots of different sizes mixed together tells how much erosion occurred -* better sorting=eroded farther

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Sorting (clastic trait 1)

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measures how spherical the grains are -well rounded --very spherical -moderately rounded --somewhat spherical -poorly rounded --grains are jagged, angular, blocky *longer transport=more round

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Roundness (clastic trait 2)

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moderately rounded gravels (clastic)

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Conglomerate

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poorly rounded gravels (clastic)

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breccia

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sand (clastic)

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sandstones

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silt (clastic)

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siltstone

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layered clay (clastic)

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shale

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unlayered clay (clastic)

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mudstone

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form via chem reaction. thick layers. -ex: bonneville salt flats in Utah *sorting and rounding don't apply to chem seds -usually comprised of 1 major mineral type

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chemical sediments

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rock salt (chem sed)

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halite

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rock gypsum (chem sed)

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gypsum

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chert (chem sed)

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quartz

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composed of plant and animal remains classified by the types of materials present

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Biogenic

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tiny carbonate shells poorly cemented together (bio seds)

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chalk

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carbonate particles (bio seds)

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limestone

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compressed plant remains (bio seds)

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coal

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1. lack of consolidation 2. slope steepness 3. moisture level 4. amt of vegetation

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What causes land slides

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cohesive forces bind sediment -ex: plant roots consolidate seds -- this is why there is small dirt when pull a plant out the ground

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Lack of consolidation (landslides)

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the max angle at which a slope is stable -often marked at 35* but it can vary so don't assume

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angle repose

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too little water -dry grains roll downhill --ex: building a sandcastle with dry sand too much water -seds turn to mud and flow downhill easily moderate amount of moisture -adds cohesive force that holds grains in place

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moisture level (landslides)

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usually stabilizes but it can destabilize -lots of veg can soak up lots of water --water dries up seds and adds weight to the slope --roots also help water flow deeper into the slope and saturate it you want a moderate amt of veg

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amount of vegetation (landslides)

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based on type or material moving and the type of movement

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Mass wasting

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type of material: solid rock type of movement: fell straight down

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Rockfall

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material: rock movement: sliding downhill -slides move slower due to friction but they cover long distances ex: mudslides, snow, avalanches

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rockslide

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gradual downhill movement of sediments due to gravity

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creep

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-unstable slopes do not occur automatically -earthquakes -over saturation -anthropogenic

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what causes masting

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grading slopes to early -landscaping past the angle of repose can destabilize removing vegetive cover -clear-cutting exposes the soil and the roots no longer help hold seds in place

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anthropogenic

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1. building codes 2. drainage control 3. decrease slope grades 4. retains walls 5. rock belts

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prevention

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knew nearby slopes are unstable but they prolonger it so long that it cost 200 million dollars in damage

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Case Study: Thistle, Utah

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new study says hot spots activity in some areas slower than previously thought

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Geology in the news (Lecture 6)

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rate of increasing temperature while increasing depth in the Earth's interior -Avg: 30° C/km -typical range 20-60° C/km -metamorphism via Heat

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Geothermal Gradient

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increasing the temperature and changing rock, low pressure -over a short time scale

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1. Contact metamorphism

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1 bar = atmospheric press at surface

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pascals and bars

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~300 bar / km depth increase pressure and low temperature

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Pressure gradient

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Squeezing an object evenly from all directions -ex: squeezing play dough with your hand because the same

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Confining Pressure

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Most pressure coming from one direction (Usually top and bottom) -ex: put play dough btw hands to create a flat pressure

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Directed Pressure (AKA Differential)

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metamorphism affecting rocks over an extensive area as a result of the large-scale action of pressure -happens at a subduction zone

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2. Regional Metamorphism

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Can't pass each other easily grinding against each other -metamorphism can happen along fault by pressure change on a small scale

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3. Fault Metamorphism

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rock interacting with hot ground water -dissolving material some grow in place

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4. Metasomatism

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Economically important; high concentration of something valuable

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Ore deposits

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hot seawater that circulates through newly formed igneous rock, flushes out some old materials, brings in new, alters mineralogy and creates a new rock

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Seafloor Metamorphism

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how much did they change based on temp and pressure -trying to heat something up

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metamorphic grade

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Relativity narrow range of temperature, helps identify the temperature it was when changed

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Index Minerals

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Group of index minerals

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metamorphic Facies

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rock deeper and exposing to higher temperature pressure and INCREASING

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Prograde

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Pressure and temperature DECREASING, heading to the surface (think things back in time (retro) are trying to become hip again)

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Retrograde

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Some minerals can't be formed in certain temperature and the changes in minerals show this

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Changes w/in minerals can record P-T changes

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Layers of sheets present in the rock because of pressure (Directed pressure) ex: slate, schist, gneiss

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Foliated Metamorphic Rocks

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No layers, confining pressure, o Hornfels: o Quartzite: o Marble:

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Non-Foliated Metamorphic Rocks

question

Very fine grains

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Slate

question

Can see more of the grains/crystals: Appearance and mineralogy can be very different and hard to identify sometimes

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Schist

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Color coded layers

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Gneiss

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high temp low pressure

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hornfels

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reacts with acid

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marble

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35,000 evacuating bali as mount Laguna shows warning signs of an upcoming eruption

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Geology in the News (Lecture 6 PT 2)

question

Pulling in opposite directions, material is experiencing tension, think tug of war -divergent plate boundary

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1. Tensional

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Squeezing in on both sides, exact opposite of Tensional, flattening -convergent boundaries

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2. Compressional

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Sliding past each other -transform boundaries

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3. Shearing

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no big change when force is applied but breaks

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brittle

question

when rocks bend or flow (like clay)

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ductile (plastic)

question

rock type temperature and pressure speed of deformation -how faster force move brittle response

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responses to stress is based on

question

Rock is responding in a ductile fashion to a compressional force, Can happen on different scales

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Folds

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where rock are still realitivly straight

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limb

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point where rock bends at

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Hinge

question

Rainbow shaped

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Antiform

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Smile shaped

answer

Synform

question

Turned on its side

answer

Overturned (Antiform, Syniform):

question

Oldest layer is inner part

answer

Anticline

question

Oldest layer is outer part

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Syncline

question

Pressure left and right and compresses it, looks normal from most sides

answer

Horizontal

question

As you fold the layers they get tilted, see different and distinct patterns most common

answer

Plunging

question

Crack in the rock in response to tectonic forces -occurs in sets most common

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joints

question

Joint with motion on either side

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Faults

question

vertical fault cross section

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dip slip fault

question

the block positioned under the fault -narrow at top and wide at bottom

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Foot wall

question

the block positioned over the fault -wide at top and narrows

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Hanging wall

question

the block above the fault moves down relative to the block below the fault. This fault motion is caused by tensional forces and results in extension. (foot wall narrow top and wide bottom and hanging wall wide at top and narrows)

answer

Normal (dip slip) fault

question

the block above the fault moves up relative to the block below the fault. This fault motion is caused by compressional forces and results in shortening

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Reverse (dip slip) fault

question

Really flat, angle maybe 5 degrees • Around subduction zones -hanging up foot down

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Thrust fault

question

horizontal movement -no footwall -look at map view and not cross section

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strike slip faults

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Strike-slip fault looks like its moving to the left

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Left-Lateral

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Strike-slip fault Looks like moving right

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Right-Lateral

question

update in bail evacuation many people (75,000)

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Geology in the news (lecture 7)

question

time 1 -stressfriction --cycle starts over again

answer

what causes earthquakes

question

rocks trying to give a little bit to get pressure off (happens during time 2 of earthquake)

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elastic deformation

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Release of energy that built up as rocks try to move past one another along a fault (or plate margin)

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Earthquake

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the spot on the fault where movement actually occurs

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Focus

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The point on the surface directly above the focus

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Epicenter

question

smaller movements before the quake.

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Foreshocks

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smaller movements after the quake.

answer

Aftershocks

question

-- These are compressional waves, so they do not cause vertical or lateral movements -- Fastest Seismic waves: 6 km/s in the crust = 20x > sound waves in air --Move through solids & liquids

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Primary (P) Waves

question

-- Cause vertical displacement -- Slower, move at ~ half the speed of P-waves -- Cannot move through fluid --Ex: cannot pass through the outer core of the earth b/c it's too ductile

answer

Secondary (S) Waves

question

-- Little slower than S-waves -- Restricted to near earth's surface -- Cause vertical and horizontal movement

answer

L (long, surface) Waves

question

Their speed is affected by the materials they pass through ; come in contact with

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Seismic waves are used to study earth's interior

question

-- S-waves cannot pass through the outer core, so only P-waves pass through the core --Only P-waves are observed on the side of the earth opposite the focus

answer

S wave shadow zone

question

device used to record seismic waves.

answer

Seismometer

question

the graph produced by the seismometer Used to determine exactly when each type of seismic wave reached the seismometer

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Seismograph (-gram)

question

-- measures the amount of property damage --Uses Roman numerals Ex: II = very minor, XII = major --Useful for insurance adjustors, construction issues, etc --Not used by scientists

answer

Mercalli Index

question

--Measures the amount of ground shaking as measured by the seismometer --Created in 1935 It's a logarithmic scale

answer

Richter Scale

question

-- Measures the area of slip on the fault line = energy released ---how much did rocks move at the focus -- This is the scale scientists use most often, not the Richter scale!

answer

Moment (aka Moment magnitude)

question

-- more accurate -- easier to calculate from seismographs -- can calculate from field measurements even when no seismograph data is available

answer

Advantages of Moment magnitude

question

1-Most quakes occur along plate boundaries 2- Quakes w/ deep foci often occur at subduction zones 3- Some quakes do occur far from the edges of the plates

answer

Distribution of earthquake focus

question

1- Land use Policies Ex: Do not build directly on fault lines (In 1972 California outlawed building on a fault) 2- Follow safe Building Codes Ex: use reinforced concrete in high-risk areas 3- Build on the right type of material Myth- Don't build on solid rock b/c the ground will open & swallow your house Fact- Solid rock is one of the safest things to build on

answer

Damage Control

question

when sand/silt sediment turns into mud and begins to sink

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liquefaction

question

New Zealand quake recently triggered 'slow slip' quake -this happened after the earthquake which is uncommon

answer

Geology in the News (Lecture 8)

question

put things in order of events (Fish came before T Rex) -Qualitative easier and cheaper -youngest to oldest

answer

Relative Dating

question

Remains of ancient plants and animals, any evidence of ancient life -sedimentary rocks

answer

Fossils

question

Area in geology in studying the strata- layers of the earth

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Stratigraphy

question

breaks/gaps in the stratigraphic record of time in the layers, non continuous (Very Common)

answer

Unconformities

question

same general category of rock above and below -ex: ig rock above and below

answer

Disconformity (type of unconformities)

question

don't have same rock type above and below -ex: shale and basalt -sed then ig

answer

Nonconformity

question

looking at tilt and orientation of rock ex: layers bottom then tilt then erode

answer

Angular Unconformity

question

When you first form layers of rocks, they form horizontally

answer

Principle of Original Horizontality

question

When you have a bunch of layers stacked together, Youngest on top Oldest on bottom

answer

Principle of Superposition

question

When you have two features that intersect, thing that cuts through is the youngest

answer

Principle of Cross-Cutting

question

Fossils you find in rock layers will be in certain sequences: Oldest organisms in oldest rock, Youngest in youngest rock

answer

Principle of Faunal Succession

question

Link the areas together to see how they compare, Very powerful tool

answer

Correlation

question

Represents a very short and specific time span, needs to meet certain criteria

answer

Index Fossils

question

• Very Numerous: Large Population- Not many organisms fossilize so large population needed • Widespread: You want to go through lots of different areas and find these fossils- easier to correlate • Went extinct quickly: time span short • Easy to identify- Not sure about identification it could throw you completely off

answer

Criteria for Index Fossils

question

Correlate based on the type of rock layers

answer

Lithostratigraphy

question

-can be found in multiple places Great for coastal environments -oil and gas deposits

answer

Sequence Stratigraphy

question

o Chemical markers that lets you correlate areas

answer

Chemostratigraphy

question

Magnetic reversals where you can compare the sequences of the reversals and correlate them

answer

Magnetostratigraphy

question

4.5 Ga- 4.0 Ga (Disputed) • Planet Accretion, Theia Impact, Forming primitive atmosphere and ocean

answer

1st Eon: Hadean

question

4 Ga- 2.5 Ga • Start building more continental crusts -oldest signs of life

answer

2nd Eon: Archaen

question

2.5 Ga- 550 Ma • Oxygen starts to come into atmosphere

answer

3rd Eon: Proterozoic

question

550 Ma- Now Most life starts to form 3 Eras

answer

4th Eon: Phanerozoic

question

550 Ma- 200 Ma

answer

Paleozoic (Phanerozoic)

question

Big diversity of organisms being fossilized

answer

Cambrian Explosion (Phanerozoic)

question

200 Ma- 65 Ma -dinosaurs dominate

answer

Mesozoic (Phanerozoic)

question

65 Ma- Now o Age of mammals o After dinosaurs die out, they diversify and become bigger o Ice age

answer

Cenozoic (Phanerozoic)

question

"young" diamonds discovered -1.1 GA -very rare because diamonds have a specific temperature/pressure -indicates superhot volcanism at relatively young point in Earth history

answer

Geology in the new ( lecture 8 part 2)

question

Quantitative hard and expensive -putting numbers on everything

answer

Absolute Dating

question

thin layers of sediments that form in specific environments -only form in large bodies of water --light layers (warm part of year) --dark layers (cold part of year) -each pair that forms is a year

answer

Varves

question

counting tree rings to find age -samples overlap and find older ages -sometimes they don't always form rings so you need think about the type of tree

answer

Dendrochronology

question

atoms of same element but different number of neutrons in nucleus

answer

Isotope

question

atoms emits radiation to become stable

answer

Radioactive decay

question

energy and particles

answer

radiation

question

unstable must decay

answer

parent

question

replaces parent -sometimes stable sometimes unstable and must decay

answer

daughter

question

list of all the daughters until it becomes stable

answer

decay series (aka chains)

question

-amount of time it takes for 50% of parent atom to decay -every element has its own half life

answer

half life

question

1. radioactive isotopes must be present in your specimen 2. needs to be able to measure the parent and daughter in specimen 3. not enough left --every parent runs out it is around 5 half life 4. closed system

answer

requirements for time

question

whatever you are studying is closed off from its surrounding -like a closed taped box nothing going in or out

answer

Closed system

question

around 5,730 half life exception to the 5 half life rule

answer

Case Study: Carbon 14

question

amount your making= amount you use

answer

steady state

question

only things that are part of the food chain

answer

Dating with carbon 14

question

[ln(Nf/No)/-0.693]*half life

answer

how to calculate age

question

1. system remains closed systems after death 2. amount c 14 has always been the same -1st problem --c 14 production varies over time --solution ---variations are small and on short time scales -2nd problem --fossil fuels but carbon in the atmosphere that changed the relative amount of carbon isotopes in the atmosphere --solution ---this can be corrected

answer

assumptions for carbon 14

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