FINAL Questions Flashcards
What is the difference between rocks and surficial materials?
a
What are the weathering processes that physically break a preexisting rock apart to form “sediment?”
a
What are the weathering processes that chemically break down preexisting rocks?
a
How does carbonic acid form?
a
What is the chemical reaction that describes the dissolution of the mineral calcite?
a
The orientation of cave passageways in limestone and other soluble rocks is controlled by what structures?
joints
Why does dissolution occur along these structures?
a
What is meant by the term “Karst?”
cave and hydrology below ground water system
Why is there little surface drainage (e.g. rivers) in areas underlain by soluble rock?
water flows underground
How do sinkholes form? How might you recognize a sinkhole?
underground is eroded, sinkholes will appear as rounded depressions in the ground
Knowing that stream frequently flow into sinkholes and disappear into the cave systems underground, what are some of the consequences of dumping trash in sinkholes?
groundwater pollution
Areas where the plants, surface streams, and lakes are most affected by acid rain generally lack what what types of minerals in the surficial materials or underlying bedrock?
calcite
What happens to feldspar minerals when they are weathered by hydrolysis?
dissolves into clay and soluble quartz
What happens to the strength of rocks if they are susceptible to weathering by hydrolysis?
weakened
Why do rocks weather more quickly at corners (where 3 joints intersect) than along their faces?
more exposure
How does spheroidal weathering occur?
corners eroded away
Why are the granites in Vermont almost unweathered while the granites in some parts of Colorado are deeply weathered?
colorodo older.
What happens to an iron-magnesium-bearing mineral like pyroxene when it weathers by oxidation?
rusts
Rust is actually one of several minerals with different structural forms, but the same chemical formula. What mineral class does rust belong to?
iron-oxide-hydroxide
What happens when a sulfide mineral like pyrite weathers by oxidation?
rust
Explain the different ways that mining processes can greatly accelerate the rate at which pyrite oxidation takes place.
When coal is burned the pyrite in it oxidizes to produce sulfur dioxide which dissolves in water in the atmosphere to produce sulfuric acid, one of the sources of human-produced acid rain. mine tunnels containing pyrite expose large volumes of pyrite to oxygen and water.
What are the climatic variables that control the rate of chemical weathering?
temperature, wetness, acidic
Learn to recognize the differences between the chemical formulas for dissolution, hydrolysis, and oxidation.
a
What are some of the byproducts of chemical weathering processes, i.e. what kinds of materials are left after minerals in rocks undergo chemical weathering?
1) Are any of these useful to plants? 2) Where does the dissolved silica end up? Hint: Think about the process by which loose sediment turns into sedimentary rock. 3) Why are the soils that develop on ultramafic rocks toxic to many plants?
What are some common physical weathering processes?
frost wedging, sheeting, thermal expansion
Explain how frost wedging works.
water in cracks freezes
In what type of climate is frost wedging most effective as a physical weathering process?
New England
What processes can move weathered materials (surficial materials) once they form?
water erosion
Make a list of the different size classes of sediment (e.g. sand) based on size.
Boulder Cobble Pebble Sand Silt Clay Mud
Make a list of the different types of clastic sedimentary rock based on the size of the sediment.
Boulder Conglomerate Cobble Conglomerate Pebble Conglomerate Sandstone Siltstone Shale Mudstone
How do surficial materials (sediment) turn into sedimentary rocks?
Lithification: cemented together (by Quartz and Calcite)
Do surficial materials (sediments) need to be deeply buried to turn into sedimentary rock?
No
Compare the energy of the water currents capable of moving coarse sand versus the energy of water currents capable of moving silt sized sediment.
Higher energy to move larger particles
What are some of the environments that conglomerates are deposited in?
Streams
What are some of the environments that siltstones and shales are deposited in?
deep sea basins, low energy
What are some of the environments that sandstones are deposited in?
beach environments
What are the biochemical sedimentary rocks composed of?
Calcite from shells and skeletons. Form Limestone
What are the chemical sedimentary rocks composed of ?
Formed from concentrated inorganic ions (Slat, Halite, Gypsum Dolostone)
How does dolostone form?
Mg2+ cations (dissolved in groundwater) substitute for one of the Ca2+ cations in the original calcite, turning it into dolomite.This process is one type of RECRYSTALLIZATION.
What are some of the common evaporite minerals?
Halite (NaCl), Gypsum (CaSO4*2H2O), Anhydrite (CASO4)
Where would you go in the world today to find environments where evaporite minerals are being deposited?
Closed Basins, Salt Lake Utah
What are organic sedimentary rocks composed of?
Composed of partially decayed plant and animal remains—hydrocarbon compounds.
What types of environments do organic sedimentary rocks form in?
Peat Bogs, Tar pits
What is the difference between peat vs lignite coal vs bituminous coal?
he peat transforms first to lignite and then to bituminous (soft) coal. If the temperatures rise further (200–300°C), the bituminous coal transforms to anthracite (hard) coal.
Why are coal mines more dangerous than other types of mines?
Can catch on fire! methane, carbon monoxide, sedimentary rocks are prone to failure
What are some of the changes that allow you to see bedding in sedimentary rocks?
changes in color, grain size, mineral
What are some of the changes in the environment that sediments are deposited in that might produce changes from one layer of sediment to another?
fluctuations in water current, sea level changes,
Draw a profile of an asymmetric ripple mark and an arrow showing the direction(s) water currents were moving when this ripple mark formed.
Draw a profile of an symmetric ripple mark and an arrow showing the direction(s) water currents were moving when this ripple mark formed.
Draw a profile an an asymmetric ripple mark showing the orientation of the cross-bedding within that ripple. Include an arrow showing the direction water currents were moving at the time the ripple mark formed.
a
Why do mud cracks form in sediment containing clay minerals and not sand?
clay minerals expand when wet and shrink when dry, much like an accordion.The water is taken in between the clay mineral layers.
Some beds within the Monkton formation, the rock you looked at on your first field trip to Redstone Quarry, contain mud cracks. What is this telling you about the environment that the Monkton formation was deposited in?
alarge scale drainage basins
What types of plants or animals are most likely preserved as fossils?
hard structured calcite rich
What types of plants or animals are least likely preserved as fossils?
soft body parts without skeletons
What are the different ways that fossils can form and be preserved in rocks?
carbon film, impression, petrification, recystalization