Geology Chapter 2: Sedimentary Rocks

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Questions and Answers

How do sedimentary rocks form?

Sedimentary rocks form primarily by the deposition of sediments under water.

What are the three main types of sedimentary rocks?

Clastic, crystalline, and bioclastic

What is a clast?

A rock fragment

How are clastic sedimentary rocks formed?

By the burial, compaction, and cementation of clasts. Signup and view all the answers

How are clastic sedimentary rocks classified?

By the size and shape of the clasts they are made up of. Signup and view all the answers

What is the difference between a conglomerate and a breccia?

Conglomerates have rounded fragments and breccias have angular fragments. Signup and view all the answers

How are crystalline sedimentary rocks formed?

By the evaporation of sea water and the precipitation of solids from sea water. Signup and view all the answers

What does saturated mean?

Full of. Signup and view all the answers

Describe evaporation and precipitation.

When a shallow sea evaporates, the minerals dissolved in the water stay behind and the water becomes saturated. If the sea evaporates any more, the minerals that are dissolved will be forced to form solid crystals (precipitate). Signup and view all the answers

What does precipitation mean when we are talking about sedimentary rocks?

Precipitation is the process of solids forming in a liquid when a solution becomes too concentrated for minerals to stay dissolved. Signup and view all the answers

How are bioclastic sedimentary rocks formed?

Bioclastic sedimentary rocks form when fragments from previously living material are compacted. Signup and view all the answers

How was coal formed?

Coal is formed from the compaction of partially decayed ancient plant material. Signup and view all the answers

Describe the temperature and pressure of formation of sedimentary rocks as compared to other rock types.

Sedimentary rocks form at low temperatures and pressures compared to other rocks. Signup and view all the answers

Why are sedimentary rocks found as a veneer over much of Earth’s surface?

Because sedimentary rocks are made of materials deposited in layers at Earth's surface. Signup and view all the answers

Why aren't sedimentary rocks found deep in the Earth?

Because the higher temperatures and pressures deep in the Earth would melt or metamorphose them. Signup and view all the answers

Why are sedimentary rocks the only rocks that contain fossils?

The processes, temperatures, and pressures that form other rocks destroy or distort any fossils in them. Signup and view all the answers

Why are sedimentary rocks often layered?

Sediments are deposited in layers that are later compacted and cemented to form rock. Signup and view all the answers

Study Notes

Formation of Sedimentary Rocks

Sedimentary rocks primarily form through the deposition of sediments in water.
Layers of sediments accumulate over time, leading to rock formation.

Types of Sedimentary Rocks

Three main types include clastic, crystalline, and bioclastic.
Clastic rocks are composed of rock fragments; crystalline rocks form from evaporated sea water; bioclastic rocks comprise remnants of living materials.

Clastic Sedimentary Rocks

Clasts are fragments of rocks that make up clastic sedimentary rocks.
Formation involves burial, compaction, and cementation of these clasts.
Classification is based on the size and shape of clasts.
Conglomerates contain rounded fragments, while breccias have angular fragments.

Crystalline Sedimentary Rocks

These rocks form via the evaporation of seawater, leading to crystal precipitation.
Saturated solutions retain as much dissolved substance as possible, influencing mineral deposition.

Processes of Evaporation and Precipitation

Evaporation of shallow seas leaves behind dissolved minerals as water becomes saturated.
Excessive evaporation causes precipitation, forming solid crystals from minerals in solution.

Bioclastic Sedimentary Rocks

Formed from compaction of fragments from previously living organisms or their products.
Coal is a specific example, originating from compacted, partially decayed plant matter.

Environmental Conditions of Formation

Sedimentary rocks typically develop at low temperatures and pressures compared to igneous and metamorphic rocks.
Most sedimentary processes occur near the earth's surface, predominantly underwater.

Distribution and Characteristics of Sedimentary Rocks

Found as a veneer or surface layer over much of the Earth's terrain due to their formation from deposited layers.
Rarely located deep within the Earth, as high temperatures and pressures can cause melting or metamorphism.

Fossils in Sedimentary Rocks

Sedimentary rocks are unique in containing fossils, as the conditions for their formation preserve organic materials.
Other rock types often destroy or distort fossils during their formation processes.

Layering of Sedimentary Rocks

Layering occurs because sediments are deposited in successive layers, which are preserved during compaction and cementation.

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Description

Explore the fascinating world of sedimentary rocks with this study set. Learn how they are formed, the different types, and key concepts like clasts and clastic rocks. Perfect for students looking to deepen their understanding of geology.