Geology: Chapter 7

Almost all sedimentary rocks contain layers. Those layers can be best described by which of the following statements?

- vary in how well boundaries are defined - vary in lateral continuity - vary in thickness

Breccia and conglomerate are the coarsest types of sedimentary rocks. Match the rock type to the shape of clast.

Breccia: angular clasts Conglomerate: rounded clasts

_____ begins after sediment is buried. Pressure pushes clasts together and forces out excess water.

Compaction

Categorize both conglomerate and breccia by the depositional environments in which they would most likely form.

Conglomerate: - river - beach Breccia: - rock slide deposit - alluvial fan

Match the environmental depositional shift to its correct description.

Transgression: - the sea moves inland - facies shift towards land Regression: - facies shift away from land - the sea moves out

Loose fragments of rocks and minerals are referred to as _____.

clasts

Chemical weathering of feldspars often leads to the formation of _____ minerals.

clay

By studying ancient sedimentary rocks, scientists can better understand modern _____ processes.

environmental

Glaciers cause massive amount of _____ of the underlying material, therby producing a lot of sediment.

erosion

The most common clastic sedimentary rocks are made of the clasts that are _____.

fine grained (smaller than sand)

Because shales and siltstones are easily eroded, the areas where they are exposed typically ________.

have soft slopes and soil cover

The largest sand dunes in dry climates can stretch __________.

hundreds of kilometers

The angular clasts typical of breccia indicate what about the distance of transport?

it represent a short distance of transport

A(n) ______ is formed by the sheltering of nearshore water from wave action by a reef or islands. The sheltered water is commonly shallow, quiet, and perhaps warm.

lagoon

Travertine is a type of _____ that forms through precipitation in springs, lakes, and caves.

limestone

Sedimentary rocks are usually comprised of material that comes primarily from _____.

other locations

Turbulent, underwater masses of flowing sand, mud, and water are called _____ currents.

turbidity

Match the attribute found in sedimentary rocks to the type of information it provides.

- Bed Thickness: small or large depositional events - Color: formed on land or in the water - Clast Size: distance of transportation - Fossils: formed on land or in the water, and type of climate - Cross beds: direction of wind or water current

Match the rock with its environment of deposition. (see phone for picture)

- C (shale and limestone): shallow sea - A (red sandstone): large sand dune - B (tan sandstone with shells): beach sand - D (breccia): mountainous area

Match the sedimentary rock name with the description that is best fit.

- Conglomerate: rounded pebbles and cobbles with sand and finer particles between the larger clasts - Breccia: angular pebbles and cobbles with sand and finer particles between the larger clasts - Sandstone: sand-sized particles of varying mineral content - Siltstone: silt-sized particles, mostly containing quartz - Shale: very fine-grained clay minerals

Match the nearshore or ocean sedimentary environment to its description

- Deep Seafloor: dominated by fine dust of windblown origin and the remains of single-celled organisms - Lagoons: mixed sand and mud of fluvial origin derived from land and coral and sand from reefs - Tidal Flats: low areas alternately covered by water and exposed to the air - Barrier Island: long, narrow accumulation of sand located parallel and near to the shoreline

Chemical reactions affect a rock by breaking down its minerals, causing new minerals to form, or by removing soluble material from the rock. Those reactions include _____.

- biological reactions - oxidation - dissolution - hydrolysis

Identify from the following list possible environments or conditions that can lead to the formation of clay or silt deposits

- chemical weathering of soils - windblown material generated by glaciers - floodplains of river systems - bottoms of lakes

Which of these rock types are clastic sedimentary rocks?

- conglomerate - sandstone - shale

What are the three types of beds formed by sedimentary layers?

- cross - graded - parallel

Match the type of chemical weathering with the best example.

- dissolution: soluble minerals break apart in a weak acid - oxidation: metal rust forms from some minerals containing iron - hydrolysis: clay minerals form from silicate minerals exposed to a weak acid - biological reactions: bacteria consume parts of some rocks

Earth materials that are soluble in water or react to a weak acid commonly have what type of appearance?

- grooved - pitted

Match the resource found in sedimentary rocks with its most common, current societal use.

- groundwater: fresh supplies essential to life - petroleum: transportation and energy - coal: electrical energy - salt: food, medicine, industry - limestone (cement): construction

Limestone is formed _____ by organisms such as coral that extract calcium cabonate from the water to form their shells and skeletons.

- in reefs - in seawater - in oceans

Sedimentary environments on land differ because of variations in _____.

- local geology - topography - amount of water

Most of the material contained within nonclastic sedimentary rocks consists of __________.

- materials formed through biological activity such as making shells or other hard parts - minerals precipitated from solution as water evaporates

Compaction causes sediment to become _____.

- more compact - more dense

Match the sedimentary environment to the description that best fits it.

- mountain: steep gradients, vigorous erosion, and fluvial systems confined by bedrock - dry climates: wind moving sand and fine particles and forming large sand dunes - delta: formed by sediments piling up where a river enters a standing body of water - wet environments: soil saturated by water with vegetation adding to the available sediment

A sandstone with a history that can be traced to beach deposits will likely include sand and _____.

- pebbles and larger clasts - pieces of shells

Match the nonclastic sedimentary rock with the process by which it typically forms.

- rock salt and gypsum: evaporation - dolostone: chemical replacement - chert and iron-rich formations: precipitation

Which of these resources are contained in sedimentary rocks?

- salt - water - coal - uranium

Match the predominant sediment size to its rock type.

- silt: siltstone - clay: shale - silt mixed with clay: mudstone

Identify the factors that strongly influence the size, shape and/or sorting of sedimentary clasts.

- strength of current - sediment supply - steepness of slope - agents of transport

The four major causes of physical weathering are _____.

- thermal expansion - near-surface weathering - frost and mineral wedging - biological activity

Which of the following processes would be most likely to form the well-rounded clasts found in a conglomerate rock sample?

- wave action along a beach - a long distance of transport

Place in correct vertical order the sedimentary facies created during a sea regression.

1.) beach sandstone 2.) mud 3.) limestone

Rank the particle sizes from smallest to largest.

1.) clay 2.) silt 3.) sand 4.) pebble 5.) cobble 6.) boulder

Place in order the sedimentary facies created during a sea transgression. Put the layer as you would see them in cross section, with the layer formed first on the bottom and the youngest layer on top.

1.) limestone 2.) mudstone 3.) sandstone 4.) bedrock with erosional surface

A formation is defined as ____.

A rock unit that is distinct and laterally traceable

_____ is the term used to describe the size range of clasts in a sedimentary deposit or rock.

Sorting

Loose sand on the continental shelf or shelf slope that becomes unstable and flows downslope as a thick slurry of sediment and water is known as _____.

a turbidity current

Shallow coastal accumilations of sand that rise above the sea as long, narrow islands are called _____.

barrier islands

Limestone and other related sedimentary rocks are also called _____ rocks because they are composed of carbonate ions bonded to other elements.

carbonate

A soft, very fine-grained limestone formed via the accumulation of the calcium carbonate remains of microorganisms is known as _____.

chalk

This type of carbonate rock is formed when magnesium replaces calcium in limestone to form a different mineral.

dolostone

Carbonate rocks found in _____ environments are commonly massive, gray in color, and are erosion-resistant, whereas carbonate rocks found in _____ environments are often pitted, holey, and very fractured.

dry; wet

The contact between the shale, which dominates the bottom part of this sedimentary sequence, and the sandstone, which dominates the upper part, is best described as _____.

gradational

Streams and rivers located in the ______ are characterized by steep gradients and bedrock canyons.

mountains

The two main processes by which sediment is produced are _____.

physical and chemical weathering

Sediment is often formed from ions in solution. The ions are _____ by inorganic chemical reactions or biological activity.

precipitated

In warm, shallow, marine environments, corals and other marine life typically construct ____.

reefs

A(n) _____ occurs when the sea retreats because sea level drops and/or land is uplifted.

regression

Different environments tend to produce sandstones that _____.

reveal clues about their differing origins

As boulders are moved downstream and weathering breaks them into smaller clasts, they first become cobbles, then pebbles, and finally _____ or smaller particles.

sand

Sandstone is defined by being mostly or wholly composed of _____-sized grains.

sand

Sandstone is common because _____.

sand occurs in many environments

Most of the exposed surface of Earth is covered with _____.

sediment and sedimentary rock

Clastic sedimentary rocks are classified primarily on the basis of _____.

sediment size

Loose sediment hardens, or lithifies, into _____ rocks.

sedimentary

The _____ of a sediment particle is affected by transportation as abrasion removes the rough edges and creates a rounder fragment.

shape

The pieces of rock that collect at the bottom of steep slopes are known as _____.

talus

Geologists use characteristics such as bedding, mudcracks, and color preserved in sedimentary rocks to determine _____.

the environment in which the rocks were deposited

Fluvial refers to _____.

the processes and sediment of streams and rivers

The _____ of a sea across a region that was previously dry is caused by a rise in sea level and/or the lowering of the land surface.

transgression

Clastic sedimentary rocks are usually comprised of sediment that comes mainly from other locations.

true

The cross beds shown here indicate what about the environment the sandstone was deposited in?

water/wind flowed from right to left