Geology Basics Quiz

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Questions and Answers

What three characteristics do geologists use to identify a rock sample?

Color, texture, and mineral composition.

What are the three groups into which geologists classify rocks?

Igneous rock, sedimentary rock, and metamorphic rock.

What is a rock's texture?

The look and feel of the rock's surface.

What methods do geologists use to determine the mineral composition of a rock?

Microscopic observation, acid testing, and magnet testing. Signup and view all the answers

What do the three major groups of rocks have in common? How are they different?

All three groups are composed of minerals but form in different ways. Signup and view all the answers

What are the three major characteristics that geologists use to identify igneous rocks?

Origin, texture, and mineral composition. Signup and view all the answers

What is the difference between extrusive and intrusive rocks? Give an example of each.

Extrusive rocks form from lava on the surface (e.g., basalt) while intrusive rocks form from magma beneath the surface (e.g., granite). Signup and view all the answers

Explain what causes an igneous rock to have a fine-grained or coarse-grained texture.

The texture depends on the cooling rate of the rock; rapid cooling leads to fine-grained texture and slow cooling leads to coarse-grained texture. Signup and view all the answers

Why are some igneous rocks dark and others light?

Rocks low in silica are dark (e.g., basalt) while those high in silica are light (e.g., granite). Signup and view all the answers

How are basalt and granite different in their origin, texture, and mineral composition? How are they similar?

Basalt forms from lava and is fine-grained, while granite forms from magma and is coarse-grained. Signup and view all the answers

Once sediment has been deposited, what processes change it into sedimentary rock?

Compaction and cementation. Signup and view all the answers

What are the three major kinds of sedimentary rocks?

Clastic rocks, organic rocks, and chemical rocks. Signup and view all the answers

Describe two ways in which limestone can form.

From the compaction of shell fragments or from dissolved calcite that cements the shell particles together. Signup and view all the answers

Compare and contrast shale and sandstone. Include what they are made of and how they form.

Shale is made of clay particles and forms from compaction, while sandstone is made of sand and quartz and forms from compaction and cementation. Signup and view all the answers

Explain how coral reefs form.

Coral animals absorb calcium, which forms their skeletons after death, leading to reef growth. Signup and view all the answers

How does coral become limestone?

Coral buried by sediments can turn into limestone over time. Signup and view all the answers

Why are living coral animals only found in water that is less than 40 meters deep?

Coral requires light for algae growth, which is insufficient below 40 meters. Signup and view all the answers

Would you expect to find coral reefs growing in the ocean near the mouth of the Amazon? Explain your answer.

No, because the water is low in salt and high in sediment, which prevents coral growth. Signup and view all the answers

Describe the process by which metamorphic rocks form.

Metamorphic rocks form through heat and pressure that change existing rocks into new minerals. Signup and view all the answers

What characteristics are used to classify metamorphic rocks?

The arrangement of the grains that make up the rocks. Signup and view all the answers

Which properties of a rock may change as the rock becomes metamorphic?

Appearance, texture, crystal structure, and mineral content. Signup and view all the answers

How does pressure change rock?

Pressure can flatten grains and create a foliated texture. Signup and view all the answers

Why are you less likely to find fossils in metamorphic rocks than in sedimentary rocks?

The heat and pressure involved in forming metamorphic rocks can destroy fossils. Signup and view all the answers

What process gradually changes rocks from one form to another?

The rock cycle. Signup and view all the answers

How can plate movements move rocks through the rock cycle?

Plate movements push rocks into the mantle to melt and also cause crustal shifts. Signup and view all the answers

What rock comes before quartzite in the rock cycle? What rock or rocks could come just after quartzite in the rock cycle?

Sandstone comes before quartzite; quartzite could become sedimentary or igneous rock after erosion or melting. Signup and view all the answers

Begin with a grain of sand on a beach. Describe what happens as you follow the grain through the rock cycle until it returns to a beach as a grain of sand again.

The sand becomes sandstone, subducts, melts into magma, forms granite, breaks off, and returns to the beach as sand. Signup and view all the answers

In your opinion, at what point does the rock cycle really begin? Give reasons to your answer.

Magma is the starting point of the rock cycle because it crystallizes into igneous rock. Signup and view all the answers

Study Notes

Rock Identification

Geologists identify rock samples by observing color, texture, and mineral composition.
Rock texture refers to the appearance and feel of a rock's surface, particularly its grains.

Rock Classification

Rocks are classified into three major groups: igneous, sedimentary, and metamorphic.
Igneous rocks form from the cooling of molten rock; sedimentary rocks arise from compaction and cementation of particles; metamorphic rocks emerge from existing rocks altered by heat and pressure.

Igneous Rocks

Characteristics to identify igneous rocks include origin, texture, and mineral composition.
Extrusive rocks, like basalt, form from lava on Earth's surface; intrusive rocks, like granite, form from magma cooling underground.
Texture varies based on cooling rates: rapid cooling creates fine-grained textures, while slow cooling results in coarse-grained textures.

Basalt vs. Granite

Basalt is fine-grained and lacks quartz, primarily composed of feldspar and dark minerals; granite is coarse-grained, includes quartz, feldspar, and mica, and forms the cores of mountain ranges.

Sedimentary Rocks

Sedimentary rocks are categorized into clastic (formed from fragments), organic (from living organisms), and chemical (from mineral precipitation).
Limestone forms from calcite, precipitating from shells; shale consists of compacted clay particles while sandstone derives from cemented sand and quartz particles.

Coral Reefs Formation

Coral reefs grow as coral animals produce calcite skeletons; these accumulate over time, layering and forming robust structures that can extend significantly.
Living coral thrives in waters less than 40 meters deep due to light requirements for symbiotic algae.

Metamorphic Rocks

Formed by intense pressure and temperature altering the original rock structure, changing texture and mineral content.
Foliated metamorphic rocks exhibit grain arrangement in parallel layers or bands.

Rock Cycle Dynamics

The rock cycle represents continuous processes transforming rocks among igneous, sedimentary, and metamorphic types.
Plate tectonics drive the cycle, facilitating rock melting, uplift, and erosion.

From Sand to Sandstone and Beyond

Sand transitions from beaches to sandstone, then subducted into the mantle to become magma, which may cool to form granite, erode back into sand, and repeat the cycle.

Conclusion on Rock Cycle's Start

The rock cycle begins with magma; volcanic processes influence the Earth's geology, leading to various rock formations and transitions through these processes.

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Description

Test your understanding of fundamental geology concepts, including rock characteristics, classifications, and textures. This quiz will help reinforce your knowledge of the three major types of rocks and what geologists look for when identifying rock samples.