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44 Cards in this Set

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  • Back
What are Alluvial Fans?
They are wedges of sediment that are deposited by rivers and mudflows emerging from mountains onto a plain or basin.
How are floodplains of meandering rivers and alluvial fans alike?
They may both have large quantities of sediment
Where do floodplains occur?
In lowlands
What kind of environment are the floodplains in?
A fluvial environment (below water, or affected by water assumably)
Where can extensive sand dunes be found?
Mostly in deserts, but relevant for this chapter because they can also be found along coastal environments (beach and bar environments).
What is a "beach and bar" environment?
A coastal environment
Can lakes occur in desert regions?
Yes they can.
What are playa lakes?
Ephermal lakes that are formed by heavy runoff from sudden rainstorms. They often evaporate completely leaving dry lake beds.
What kinds of minerals do playa lakes leave on their dry lake beds once they have evaporated?
They leave clay and evaporate minerals such as gypsum and halite.
What is a paludal environment?
A large, swampy environment
where can one find paludal environments?
They are likely to be coastal but may also border the floodplains of some rivers.
What are Transitional Environments marked by or characterized by?
They are marked by the interaction of fluvial and oceanic processes.
What are Deltas?
Deltas are deposits of sediments carried by river systems to the ocean. They are of such large quantities that they are generally unaffected by the erosional action of tides, waves or currents.
What are three types of specific transitional environments?
Beaches, tidal flats and bars; they are affected by the tidal cycle of the oceans and, in some cases, by the action of the wind.
What are broad categories of marine environments?
Shall marine environments and deep marine environments
What is the maximum depth of a "shallow" marine environment?
200 meters... it must be less than 200 meters to be considered shallow
What is the general range of deep marine environments?
How deep does wave turbulence extend?
15 meters
Why is the sediment in the shallow water the coarsest.
Because everything else is carried away by all the turbulence; only the coarsest grains can settle to the bottom.
Can coarse sediment ever be carried to great depths?
Yes, if it is really deep close to land... but not if the great depths are farther from land.
What CAN be deposited in the great depths that are further away from the shore?
Only very fine clay particles, wind-blown volcanic ash, and the skeletons of microscopic marine plants and animals settle on the ocean floor.
What can turbidity currents do?
They can transfer sediment that has already been deposited close to the coastline further out in the deeper water of the continental rise or as far out as into the actual abyssal plains
Where are limestones (either fossiliferous or crystalline) mainly formed?
On shallow continental shelves where there is little to no terrigenous sediment input from rivers or turbidity currents. Basically on the shelves where there isn't sediment from land come in to interfere with it and where there aren't currents that are going to prevent the limestone from lithifying.
What are other important contraints other than sediment influx that can mess with the formation of limestones?
Water temperature and salinity; it needs to be relatively warm because limestones are only found in the equatorial zones from 30 degrees north to 30 degrees south
How deep does the continental shelf generally extend?
About 200 meters deep, going out at an incline of about 0.1 degrees.
What is the continental slope and what is its actual slope?
Its slope (or inclination) is about 4 degrees, and it is the area at which the continental shelf abruptly decreases its slope and goes down quicker.
Where are reefs typically found?
They are often present on the continental shelf, but rarely on the shelf edge
What is Bedding, or Stratification?
The most obvious feature of sedimentary rocks in an outcrop. It results from a change in grain size, color or rock type from one bed to the next and its usually more obvious in a weathered outcrop than a fresh one.
Where is the continental shelf likely to be narrow?
Along mountainous, pacific-type coasts. Furthermore, mountains chains or island arcs may occur in ocean basins or on a continental border and deep linear subduction trenches usually adjoin them.
What is bioturbation?
It is when organisms burrow, churn and stir the original sediment so that the finer laminations and bedding are destroyed.
What are the essential properties of a bed?
Its thickness and lateral continuity
What are the ranges for a thick, medium and thin bed?
Thick = >61 cm
Medium= 5-61 cm
Thin = 1.5-5cm
What would a laterally uniform bed look like?
It would continue for tens or hundreds of meters without much change in thickness
What would a laterally variable bed look like ?
It would change in thickness over several to tens of meters.
What are the two categories of bedding in undeformed sedimentary rocks?
1) Planar
2) Cross-stratified
What is plane bedding?
A type of bedding that can be formed in any kind of environment. These beds are often laterally extensive and commonly thinly laminated.
What is cross-bedding?
Cross bedding, or cross stratified bedding, is an arrangement of the beds in which one set is inclined relative to the others.
What does cross-bedding indicate?
It indicates the action of strong currents of water, as in river or the shallow marine environments, or of wind.
How can the direction of the inclination of cross-bedding be useful?
It can tell us what direction the current (water or air) flowed
What are the two types of cross-bedding?
1) Tabular-Planar cross-bedding
2) Trough cross-bedding
Where is Tabular-Planar Cross-bedding found?
It is seen in beach deposits and dunes. Do not confuse it with the tabular-planar crossbedding that is carried out by wind (which is called Aeolian cross-bedding)
Where is trough cross-bedding found?
In river and stream channels
What are the foreset beds ?
They are the inclined layers
What is graded bedding?
Repeated beds, each of which has the coarsest grains at the base of the bed