Sedimentary Rock Quiz

What percentage of land areas are covered by sediments and sedimentary rocks?

75%

What does a dark red color in a sedimentary rock mean?

iron-oxide is present hematite rust.

Grains

sand, fossils, ooids, etc.

What is the mineral composition of bioclastic/organic sedimentary rocks?

- Rocks are made from material that was once alive. - Pieces of shell which are made out of calcite. - Plant remains made out of carbon.

By what process do sediments become well sorted, and by what process do sediments become poorly sorted?

- Sediments that are transported for a long, sustained time tend to become well sorted. - Sediments that are transported over a rather short period of time tend to be poorly sorted.

Shale

- Shale is formed by sand that is cemented and compacted together. It is composed of small and soft sediment that crumbles very easily when exposed to water. - Shale is deposited in a low energy enviroment, slow-moving water.

How does weathering change the shape of sediment?

- When the rock is first weathered, it is mroe sharp with jagged edges. - But, as it gets eroded more it becomes smaller, smoother and more rounded.

Angularity

- the degree of edge or corner smoothness - Angular: When the sediments are angular and not smooth.

How does particle size give us information about the environment in which they were deposited?

-The larger the particle, the more energy need for it to be carried. Larger particles are associated with quickly moving rivers, landslides, and glaciers. - Less energy is required to transport smaller particles. Small particles are associated with the quiet water of a lake, lagoon, or swamp.

What are three different ways that rocks are worn down by abrasion?

1) When glaciers move along the bottom of a body of water pulling smaller rocks along with it. The below will grind on the bottom of the water. 2) When wind carries sand, it can also cause the abrasion of rock. 3) Rivers carrying sediments are another way that rocks can be worn down.

What type of environment would a rock that is poorly sorted come from?

A landslide because sediment is deposited all at once so there is no time to sort by size or smooth out the angular grains.

Chert

A name applied to sedimentary rock composed of microcrystalline quartz that is hard and dense.

Dissolving

A process in which a solid becomes a part of a liquid to form a solution.

Frost wedging

A process of mechanical weathering in which water seeps into cracks and freezes. Because water expands when it freezes, the ice can put pressure on the rock, causing the crack to enlarge.

Cementation

A reduction in pore space by adding new mineral material that acts as a glue to bind the grains together. The grains are squeezed tightly together. The grains may begin to dissolve where contracts are under high pressure. Solutions between grains precipitate minerals that cement grains together to form a rock.

Compaction

A reduction in pore space by packing grains more tightly together. Grains are compacted together to fit more tightly. The water from the pores is squeezed out. It is most significant in fine-grained rocks such as shale.

Chemical/crystalline rocks:

A rock made of a mineral that has precipitated out of the water. Minerals can dissolve in water and then precipitate out of the water when the water evaporates.

Abrasion

A type of mechanical weathering in which the surface of a rock is scratched and physically torn away.

sedimentary rock

A type of rock that covers most of earth's surface like a thin layer of dust. Most form from the compaction and cementation of sediments (clastic/detrital.)

Coquina

A variety of limestone composed entirely of shells cemented by calcite.

How are the products of chemical weathering errored?

After weathering, the soluble constituents are dissolved and carried away by runoff and groundwater.

Natural chalk

An organic sedimentary rock composed of tiny matine anumals.

How does burial promote diagenesis?

As sediments are buried, they are subject to increasing temperatures and pressures.

What are the 6 categories of sediment sizes?

Boulder, clay, sand, silt, pebble, and cobble.

How is clastic rock weathered?

By wind water, or ice.

How are clastic rocks eroded (transported)?

By wind, ice, or gravity.

What is the mineral composition of clastic rocks?

CLASTICS ARE MOSTLY QUARTZ, FELDSPAR, CLAY AND PIECES OF ROCK.

Example of a poorly sorted rock:

Conglomerate

How are conglomerate and breccia different?

Conglomerate has rounded grains while Breccia has angular grains.

What do vertical changes in rock represent:

Environmental changes through time.

Crystalline rocks (evaporites)

Form when water evaporates from a solution causing crystals of a mineral to precipitate out of the solution. These crystals of a mineral are known as evaporates or precipitates.

What climates are affected by frost wedging?

Frost wedging is more important in a cold climate because if there is a large temperature change that the environment is not used to, then the rock will crack as the water expands.

Where is frost wedging most common?

Frost wedging is more important in a warm climate because there is a large temperature change that the environment is not used to, then the rock will crack as the water expands.

What two factors correlate to the distance that a rock has traveled?

Grain size and rounding

What does texture mean in sedimentary rocks?

How a rock formed.

How does cementation affect a rock's porosity?

It decreases because the cementing material fills up most of the pore space to glue the grains together.

What sedimentary rock can be crystalline or bioclastic?

Limestone

What type of rock is affected by dissolving, and what features result?

Limestone is the type of rock affected by dissolving because when rain mixes with carbon dioxide it forms carbonic acid. The calcium in limestone rock reacts with the calcium carbonate and causes it to dissolve.

Where are sediment and sedimentary rocks concentrated?

Near the surface; the geosphere, the hydrosphere, the atmosphere, and the biosphere.

How does deposition lead to the formation of sedimentary layers?

Older sediments are buried beneath younger layers and gradually converted into sedimentary rock by compaction and cementation.

How is coal formed?

Organic plant matter is buried in an oxygen poor environment, it evolves into peat, and then into coal.

Bioclastic/organic rocks

Pieces of dead material cemented and compacted together.

Process of Creating Coal

Plant material falls into water where it can not decay as quickly as it accumulates. Compression converts the remains to peat, which ignites and then into bituminous coal, which is relatively low in density. If it is buried deeper than it may produce the metamorphic rock anthracite.

mechanical weathering

Rocks are physically broken down.

Evaporites

Rocks formed from crystals that precipitate during evaporation of water.

Example of a well sorted rock:

Sandstone

What can scientists learn by studying sedimentary rocks?

Scientists can reconstruct the configuration of ancient landmasses and the location and continents of long-vanished mountain systems.

well sorted sediment

Sediment in a detrital rock that is primarily one grain size.

How are sediments cemented together?

Sediment is brought together by a cementing agent dissolved in water that precipitates into the pore spaces between the grains of the sediment.

poorly sorted

Sediment with a wide range of grain sizes. Sediment is deposited quickly and all at once, so there is no time to sort it by size.

Why are sedimentary rocks important?

Sedimentary rocks provide geologists with information necessary to study the history of Earth and provide various economically important resources.

How does the volume of sedimentary rocks in Earth's crust compare with the volume of igneous and metamorphic rocks?

Sedimentary rocks: cover 5-10 percent of the Earth's crust Metamorphic rocks: cover 90-95 percent of the Earth's crust

What is the best place to preserve fossils?

Shale because it is formed in low energy enviroments.

Limestone can be made out of either:

Shells or calcite.

what is the hardest cement?

Silica

how does clay formation affect a rock?

Some minerals transform into clay, which is softer than the original minerals. The clay absorbs the water expands and causes the rock to crumble.

Pores

Spaces between sediment grains. Groundwater, oil, and natural gases are found here.

Porosity

The ability of a liquid to place through. The porosity decreases as cementation occurs.

Climate

The average weather conditions in an area.

Sphericity:

The degree to which a rock fits the shape of a sphere.

Examples of chemical weathering

The dissolving of limestone and the transformation of minerals into clay.

Which of the processes listed below would transform an exposure of granite in the mountains into sedimentary rocks?

The granite would mechanically weather into small particles, which would travel down the slope of the mountain by mass movement, be deposited, and undergo diagenesis when the sediments are buried under younger layers of rock.

Clastic/Detrial Rocks

The largest type of sedimentary rock. It is made of pieces of other rocks cemented and compacted together.

Diagenesis/Lithification

The physical and chemical changes occuring during the conversion of sediment to sedimentary rock.

What causes sediment to get compacted?

The pressure form the layers on top of it.

Re-crystallization

The process in which more stable minerals are created from less stable ones.

Chemical weathering

The process that breaks down rock through chemical changes. It happens in crystalline rocks.

How can sedimentary rocks be used by historians to study past conditions at Earth's surface?

The textures, structures, and fossils in sedimentary rocks allow scientists to gain insight into past climates ecosystems, and ocean environments.

How does compaction change the orientation of sediment?

The weight of the overburden is perpendicular to the orientation of the sediment.

What do angular grains tell you about a rock?

They are close to their source.

How are weathering and erosion affected by temperature?

They generally increase in temperature as the rate of erosion and weathering increase. However, for frost weathering and dissolving, the rate of weathering/erosion is faster in colder temperatures.

What do smooth and round grains tell you about a rock?

They have traveled a great distance from their source.

Erosion

Transport

Zooplanton and phytoplankton

Two marine animals that have calcite shells.

How do weathering and erosion relate?

Weathering must happen in order for erosion to happen. Weathering starts the process of turning igneous rock into sedimentary rock by breaking down rock by water, wind, or ice. Then, erosion transports the material once it is converted into sediments by weathering.

How are atoms dissolved in solution removed?

When chemical or temperature changes cause the material to crystalize and precipitate.

How are most chemical/crystalline sedimentary rocks formed? What is this group of rock called?

When material settles out of solution in sea water as the water evaporates. As the water evaporates, salts are left behind. This group of rock is called evaporites.

Deposition

When the erosional agent (usually water) slows down to a speed that can not carry the sediment anymore.

How does deposition of solid material happen?

When wind and water currents slow down and as glacial ice melts.

limestone

a sedimentary rock made mostly of calcite

metamorphism is said to occur at temperatures:

above 200 degrees

Which of the choices below correctly describes three types of common cements in sedimentary rocks?

calcite (which effervesces in dilute acid), silica (which produces the hardest sedimentary rocks), and iron (which gives rocks a reddish color)

Matrix

find-grained, clay sized sediment.

What does texture mean in igneous rocks?

grain/crystal size

What is table salt made of

halite

What is the primary basis for distinguishing among detrital rocks?

particle size

Which are the two most common minerals in detrital rocks?

quartz and feldspar

Cementing agents

quartz, calcite, or iron oxide

What products of weathering cover the majority of the surficial land areas of the Earth's crust?

sediment and sedimentary rocks