When you classify objects, you organize them into groups based on common characteristics.

Question

What are some different ways you could classify these marbles?

What characteristics do you think scientists use to classify rocks?

Gizmo Warm-up
Rocks are classified by how they formed. The three types are:
Igneous rocks form from cooling magma or lava.
Sedimentary rocks form from the bonding of rock fragments such as sand, silt, or clay; from organic materials; and from chemicals dissolved in water.
Metamorphic rocks form when other rocks are changed by heat and pressure.
In the Rock Classification Gizmo, you will get to explore these three types of rocks. Think about how each type of rock is formed.

Fossils are the remains of ancient plants and animals. Which type of rock do you think is most likely to contain fossils?

Foliation occurs when minerals are flattened by heat and pressure. This results in a layered or banded texture. Which type of rock do you think is foliated?

Air pockets, or vesicles, can form in rapidly cooling magma or lava. In which type of rock would you expect air pockets?

Activity A:

Classifying rocks
Get the Gizmo ready:
Click Reset.

Introduction: You can classify rocks by examining characteristics such as texture. A rock’s texture is determined by the sizes, shapes, and positions of the grains that make up the rock.

Goal: Classify rocks as igneous, sedimentary, or metamorphic.

Summarize: The three groups of rocks each have unique characteristics. For example, many igneous rocks have a texture of interlocking mineral crystals. Sedimentary rocks may have distinct layers of sediments, known as strata.

To learn other characteristics of igneous, metamorphic, and sedimentary rocks, turn on Show common characteristics in the CHARACTERISTICS pane. In the table below, summarize the textures that will allow you to identify and classify these rock types.

Rock type
Characteristics
Igneous

Sedimentary

Metamorphic

Classify: Select Name on the SIMULATION pane. Move your cursor over the rock pictures. Based on what you see, classify the rocks by dragging them into the correct box on the CHARACTERISTICS tab. Record your classifications in the table below.

Rock type
Rock names
Igneous

Sedimentary

Metamorphic

Answer 1

Different Ways to Classify Marbles

1. Color: Marbles can be classified based on their colors, such as clear, blue, red, green, etc.
2. Size: Marbles can be grouped by size, such as small, medium, or large.
3. Pattern: Some marbles have swirls, stripes, or solid colors while others may have speckles or a translucent quality.
4. Material: Marbles can be made of glass, clay, or plastic, allowing classification based on material composition.
5. Shape: Although most marbles are spherical, some may be faceted or shaped differently.
6. Design: They can be classified by specific designs or themes, such as those depicting characters or patterns.

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Characteristics Scientists Use to Classify Rocks

1. Formation Process: Rocks are classified based on how they formed - igneous, sedimentary, or metamorphic.
2. Mineral Composition: The types and proportions of minerals present in a rock are crucial for classification.
3. Texture: The size, shape, and arrangement of the grains or crystals in the rock.
4. Grain Size: Variation in grain sizes can differentiate rocks (e.g., coarse-grained vs. fine-grained).
5. Color: Color may also indicate specific minerals or the rock type.
6. Fossil Content: The presence or absence of fossils can help categorize certain types of sedimentary rocks.

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Answers to Specific Questions

1. Fossils: Sedimentary rock is most likely to contain fossils, as these rocks are formed from the accumulation of sediments, including organic material.

2. Foliation: Metamorphic rocks are typically foliated due to the alignment of minerals under heat and pressure, resulting in a layered or banded appearance.

3. Air Pockets (Vesicles): Igneous rocks formed from rapidly cooling magma or lava may contain vesicles, as gas bubbles can be trapped in the solidifying rock.

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Activity A: Classifying Rocks

Summary of Textures for Rock Types

| Rock Type | Characteristics | |---------------|---------------------------------------------------| | Igneous | Interlocking mineral crystals, may have vesicles, smooth texture (depending on cooling rate) | | Sedimentary| Distinct layers (strata), may contain fossils or rounded grains, often granular or fine textures | | Metamorphic| Foliated or banded texture, may show signs of mineral alignment due to heat and pressure, usually more dense |

Classifications Based on Observations in the Simulation

| Rock Type | Rock Names | |---------------|---------------------| | Igneous | [List of igneous rock names from the Gizmo] | | Sedimentary| [List of sedimentary rock names from the Gizmo] | | Metamorphic| [List of metamorphic rock names from the Gizmo] |

(Note: The procedure of listing actual rock names would require the simulation interface to provide the specific examples.)