Rock Formation Q & A

ROCK FORMATION Multiple Choice Identify the choice that best completes the statement or answers the question.

Intrusive Rocks As magma cools, atoms and compounds in the liquid rearrange themselves into new crystals called mineral grains. Rocks form as these mineral grains grow together. Igneous Rocks Rocks that form from magma below the surface are called intrusive igneous rocks.

Magma that cools below Earth’s surface forms ________ rock. Answer?

The rock cycle shows how rock can be weathered to small rock and mineral grains. This process, which breaks rocks into smaller pieces, is called weathering . The movement of weathered material is called erosion . Where sediments are deposited, layer upon layer builds up. Pressure from the upper layers pushes down on the lower layers. If the sediments are small, they can stick together and form solid rock. This process is called compaction .

The processes involved in the rock cycle include all of the following EXCEPT _______ . Answer?

When mineral grains line up in parallel layers, the metamorphic rock is said to have a foliated texture. Two examples of foliated rocks are slate and gneiss.

3. Foliated rocks are distinguished by _____________ . Answer?

Extrusive igneous rocks are formed as lava cools on the surface of Earth. When lava flows on the surface, it is exposed to air and water, and cools quickly under these conditions.

4 . Lava that cools quickly forms __________ rocks. Answer?

Fluids, which are mostly water with dissolved elements and compounds, can react chemically with a rock and change its composition, especially when hot. Heat, pressure, and hot fluids trigger the changes. In the presence of hot, water-rich fluids, solid rock can change in mineral composition without having to melt.

5. Metamorphic rocks can be formed from all of the following EXCEPT _____________. Answer?

THE FORMATION OF MINERALS FROM SOLUTIONS

In some metamorphic rocks, layering does not occur. The mineral grains grow and rearrange, but they don’t form layers. This process produces a nonfoliated texture.

Metamorphic rocks form from igneous, sedimentary, or other metamorphic rocks. Each resulting rock can be classified according to its composition and texture. When mineral grains line up in parallel layers, the metamorphic rock is said to have a foliated texture.

6. A classification of metamorphic rocks would include whether they are _______. Answer?

Sediments are loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice, or gravity. Sediments come from already-existing rocks that are weathered and eroded. Sedimentary rock forms when sediments are pressed and cemented together, or when minerals form from solutions

75 % of the rocks exposed at the surface are sedimentary rocks. Sedimentary rocks often form as layers.

7. Sedimentary rocks are __________. Answer?

D. FORMED FROM ALREADY EXISTING ROCKS THAT ARE WEATHERED AND ERODED

Basaltic (buh SAWL tihk) igneous rocks are dense, dark-colored rocks. They form from magma that is rich in iron and magnesium and poor in silica, which is the compound SiO2.

Granitic igneous rocks are light-colored rocks of lower density than basaltic rocks. Granitic magma is thick and stiff and contains lots of silica but lesser amounts of iron and magnesium.

Andesitic igneous rocks have mineral compositions between those of basaltic and granitic rocks.

8. Andesitic rocks have mineral compositions between those of ______ and basaltic . Answer?

Matter and the Rock Cycle The rock cycle shows how rock can be weathered to small rock and mineral grains. This material then can be eroded and carried away by wind, water, or ice. This illustrates the principle of conservation of matter. The changes that take place in the rock cycle never destroy or create matter. The elements are just redistributed in other forms.

9. The changes that take place in the rock cycle ___________. Answer?

D. NEVER CREATE OR DESTROY MATTER

Detrital Sedimentary Rocks The word detrital (dih TRI tul) comes from the Latin word detritus , which means “to wear away.” Detrital sedimentary rocks are made from the broken fragments of other rocks.

10. Detrital rocks are ________. Answer?

A. MADE FROM THE FRAGMENTS OF OTHER ROCKS

11. The rock cycle indicates that each type of rock can _________. Answer?

Rocks change by many processes. For example, a sedimentary rock can change by heat and pressure to form a metamorphic rock. The metamorphic rock then can melt and later cool to form an igneous rock. The igneous rock then could be broken into fragments by weathering and erode away. (continued)

The fragments might later compact and cement together to form another sedimentary rock. Any given rock can change into any of the three major rock types. A rock even can transform into another rock of the same type.

12. Pumice, obsidian, and scoria are kinds of ___________. Answer?

Volcanic Glass Pumice, obsidian, and scoria are examples of volcanic glass. These rocks cooled so quickly that few or no mineral grains formed. Most of the atoms in these rocks are not arranged in orderly patterns, and few crystals are present. In the case of pumice and scoria, gases become trapped in the gooey molten material as it cools. Holes are left behind where the rock formed around the pockets of gas.

13. A rock is _________. Answer?

What is a rock?—Common Rocks Most rock used for building stone contains one or more common minerals, called rock-forming minerals, such as quartz, feldspar, mica, or calcite. When you look closely, the sparkles you see are individual crystals of minerals. A rock is a mixture of such minerals, rock fragments, volcanic glass, organic matter, or other natural materials.

B. A MIXTURE OF MINERALS, ORGANIC MATTER, VOLCANIC GLASS, OR OTHER MATERIALS.

14. The crystals that form in slowly cooling magma are generally _________. Answer?

Magma Because magma is less dense than surrounding solid rock, it is forced upward toward the surface. When magma reaches Earth’s surface and flows from volcanoes, it is called lava . As magma cools, atoms and compounds in the liquid rearrange themselves into new crystals called mineral grains. When cooled slowly these crystals are generally large.

15. Detrital rocks are named according to__________ . Answer?

Shape and Size of Sediments Detrital rocks have granular textures, much like granulated sugar. They are named according to the shapes and sizes of the sediments that form them.

C. THE SIZE AND SHAPE OF THERE SEDIMENTS.

16. Sedimentary rocks are usually classified as ____________. Answer?

Classifying Sedimentary Rocks Like igneous and metamorphic rocks, sedimentary rocks are classified by their composition and by the manner in which they formed. Sedimentary rocks usually are classified as detrital, chemical, or organic.

D. DETRITAL, CHEMICAL, OR ORGANIC

Matching Match the terms with their descriptions below. ______ 17. Rocks formed by changes in heat and pressure or the pressure of hot, watery fluids.

Rocks that have changed because of changes in temperature and pressure or the presence of hot watery fluids are called metamorphic rocks .

18. Rocks formed from molten materials

When hot magma cools and hardens, it forms igneous (IHG nee us) rock .

19. Rocks formed from sediments

20. Igneous rocks formed on or near the earths surface

Extrusive Rocks Extrusive igneous rocks are formed as lava cools on the surface of Earth. When lava flows on the surface, it is exposed to air and water, and cools quickly under these conditions.

Foliated Rocks When mineral grains line up in parallel layers, the metamorphic rock is said to have a foliated texture. Two examples of foliated rocks are slate and gneiss. Slate

22.Process by which sediments are pressed together to form rock.

Compaction Where sediments are deposited, layer upon layer builds up. Pressure from the upper layers pushes down on the lower layers. If the sediments are small, they can stick together and form solid rock. This process is called compaction .

23. Light colored igneous rocks with a lower density than basaltic rocks

Granitic Rocks Granitic igneous rocks are light-colored rocks of lower density than basaltic rocks. Granitic magma is thick and stiff and contains lots of silica but lesser amounts of iron and magnesium.

24. Dense, dark colored igneous rocks.

Basaltic Rocks Basaltic (buh SAWL tihk) igneous rocks are dense, dark-colored rocks. They form from magma that is rich in iron and magnesium and poor in silica, which is the compound SiO 2 . The presence of iron and magnesium in minerals in basalt gives basalt its dark color . Basaltic lava is fluid and flows freely from volcanoes in Hawaii, such as Kilauea .

25. Metamorphic rocks that don’t have layers

Nonfoliated Rocks In some metamorphic rocks, layering does not occur. The mineral grains grow and rearrange, but they don’t form layers. This process produces a nonfoliated texture.

26. Process by which large sediments are glued together by dissolved minerals to form rock

Cementation If sediments are large, like sand and pebbles, pressure alone can’t make then stick together. Large sediments have to be cemented together. As water moves through soil and rock, it picks up materials released from minerals during weathering. The resulting solution of water and dissolved materials moves through open spaces between sediments.

27. Igneous rocks formed below Earth’s surface

Intrusive Rocks As magma cools, atoms and compounds in the liquid rearrange themselves into new crystals called mineral grains. Rocks form as these mineral grains grow together. Rocks that form from magma below the surface are called intrusive igneous rocks.

28. Bits of weathered rock, minerals, grains, plants, and animals that have been eroded.

Sediments are loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice, or gravity. Sediments come from already-existing rocks that are weathered and eroded.

29. Model that illustrates the processes that create and change rocks.

To show how rocks slowly change through time, scientists have created a model called the rock cycle . It illustrates the processes that create and change rocks. The Rock Cycle

30. Magma that reaches Earth’s surface and flows from volcanoes.

Magma Because magma is less dense than surrounding solid rock, it is forced upward toward the surface. When magma reaches Earth’s surface and flows from volcanoes, it is called lava .

31. A mixture of minerals, organic matter, volcanic glass, or other materials.

A rock is a mixture of such minerals, rock fragments, volcanic glass, organic matter, or other natural materials.

Identify identify each rock as igneous, metamorphic, or sedimentary

Sandstone is a sedimentary rock that’s often composed mostly of quartz grains. When sandstone is heated under a lot of pressure, the grains of quartz grow in size and become interlocking, like the pieces of a jigsaw puzzle. The resulting rock is called quartzite.

Rock Salt When water that is rich in dissolved salt evaporates, it often deposits the mineral halite. Halite forms rock salt. Rock salt deposits can range in thickness from a few meters to more than 400 m. Companies mine these deposits because rock salt is an important resource.

Pumice, obsidian, and scoria are examples of volcanic glass. These rocks cooled so quickly that few or no mineral grains formed. Igneous Rocks Most of the atoms in these rocks are not arranged in orderly patterns, and few crystals are present.

The sedimentary rock shale will change into slate. Metamorphic Rocks As increasing pressure and temperature are applied, the slate can change into phyllite, then schist, and eventually gneiss. Slate

Limestone Calcium carbonate is carried in solution in ocean water. When calcium carbonate (CaCO 3 ) comes out of solution as calcite and its many crystals grow together, limestone forms. Limestone also can contain other minerals and sediments, but it must be at least 50 percent calcite. Limestone usually is deposited on the bottom of lakes or shallow seas.

Short answer 39. Suppose you found an igneous rock that had almost even amounts of silica, iron, and magnesium. How would you classify this rock? Why?

Andesitic Rocks Andesitic igneous rocks have mineral compositions between those of basaltic and granitic rocks. Granitic rocks contains lots of silica but lesser amounts of iron and magnesium Basaltic rocks form from magma that is rich in iron and magnesium and poor in silica

Short answer 40. How do detrital, chemical, and organic sedimentary rocks differ from one another?

Detrital rocks form by compaction and cementation of rock fragments and bits of minerals, plant, and animals. Chemical rocks form from minerals dissolved in solution and deposited after evaporation. Biochemical rocks form from the remains of once living things compacted and cemented together.

Short answer 41. Your friend challenges you to tell what you know about a rock without seeing it. You are given a one word hint: clastic What can you tell your friend about the rock?

The word clastic means that the rock has a broken texture. It could be a detrital sedimentary rock or an organic rock .

Short answer 42. What makes the rock cycle a cycle?

There is no beginning or end. Rocks Are constantly changing from one to another.

Short answer 43. What is cementation?

Cementation occurs when water soaks through rock, picking up atoms and molecules released from minerals during weathering. This solution of water and dissolved materials moves through open spaces between sediments. Minerals are deposited between the pieces of sediments, holding the particles together like glue, making a detrital sedimentary rock.

44. Use the information about igneous rocks a-d to classify each one as intrusive or extrusive and basaltic or granitic. Fill in the chart with a,b,c,d Rock a- dark colored large grains Rock b- large crystals, high percentage of silica Rock c- fine grained texture, light colored Rock d- from Hawaiian volcano area no visible crystals 4 3 granitic 2 1 basaltic intrusive extrusive

Basaltic (buh SAWL tihk) igneous rocks are dense, dark-colored rocks. Basaltic lava is fluid and flows freely from volcanoes in Hawaii, such as Kilauea. Granitic igneous rocks are light-colored rocks of lower density than basaltic rocks. Granitic magma is thick and stiff and contains lots of silica but lesser amounts of iron and magnesium.

4 B 3 C granitic 2 A 1 D basaltic intrusive extrusive

45. In a concept map, would you list basaltic lava under high silica content or low silica content.

46. In a concept map, would you list intrusive rocks under rocks that form above ground or below

Intrusive Rocks Rocks that form from magma below the surface are called intrusive igneous rocks.

Short answer 47. If you were shown one photograph of pumice and one of granite, how could you distinguish between the two rocks?

In the case of pumice and scoria, gases become trapped in the gooey molten material as it cools. Holes are left behind where the rock formed around the pockets of gas. These rocks cooled so quickly that few or no mineral grains formed.

When you look closely, the sparkles you see are individual crystals of minerals. Granite has visible crystals.

Granite has visible crystals; pumice has no visible mineral grains and is full of holes.

For each item, tell which would occur first. 48. Molten material cools and forms igneous rocks. Lava flows from a volcano

Formation of Igneous Rocks When some volcanoes erupt, they eject a flow of molten rock material. Molten rock material, called magma, flows when it is hot and becomes solid when it cools. When hot magma cools and hardens, it forms igneous (IHG nee us) rock .

49. Gneiss is formed. The mineral grains in granite are flattened under pressure.

Heat and Pressure Metamorphic Rocks Schist also can form when basalt is metamorphosed, or changed, and gneiss can come from granite.

The mineral grains in granite are flattened under pressure.

Short answer 50. Describe the differences among detrital, chemical, and organic rocks.

Detrital, chemical, and organic rocks are all sedimentary rocks, but they form in different ways. Detrital rocks are made from broken fragments of rocks. These sediments are compacted and cemented together. Chemical sedimentary rocks form when minerals are precipitated from a solution or are left behind when a solution evaporates. Organic rocks form from the remains of once living things.

Short answer 51. Where does the rock cycle begin?

It has no beginning; rocks are constantly changing from one type to another.

True or false rewrite false statements to make them correct. 52. The composition of a sedimentary rock depends upon the composition of the rocks and living things its sediments came from.

Classifying Sedimentary Rocks Sedimentary rocks can be made of just about any material found in nature. Sediments come from weathered and eroded igneous, metamorphic, and sedimentary rocks. Sediments also come from the remains of some organisms. The composition of a sedimentary rock depends upon the composition of the sediments from which it formed.

53. All igneous rocks have the same mineral compositions.

Classifying Igneous Rocks The type of magma that cools to form an igneous rock determines important chemical and physical properties of that rock. These include mineral composition, density, color, and melting temperature.

False, igneous rocks are formed from three basic types of lava basaltic, andesic, and granitic

54. Nonfoliated rocks have very narrow layering.

When mineral grains line up in parallel layers, the metamorphic rock is said to have a foliated texture. The mineral grains grow and rearrange, but they don’t form layers, the metamorphic rock is said to have a nonfoliated texture.

False, foliated rocks have tightly pressed together layers (or) nonfoliated rocks have no layers

55. Sedimentary rock can be formed from changes in igneous rock, but igneous rock cannot be formed from changes in sedimentary rock.

Any given rock can change into any of the three major rock types. A rock even can transform into another rock of the same type.

False, sedimentary rock can form from changes in igneous rock; igneous rock can form from changes in sedimentary rock .

56. Metamorphic rocks can form from other metamorphic rocks.

Metamorphic rocks can form from igneous, sedimentary, or other metamorphic rocks .

Rock Formation Q & A

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