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2nd Grade Science Content Standards: Earth Sciences3. Earth is made of materials that have distinct properties and provide

resources for human activities.

B. Students know smaller rocks come from the breakage andweathering of larger rocks.D. Students know that fossils provide evidence about the plants and

animals that lived long ago and that scientists learn about the pasthistory of Earth by studying fossils.

2nd Grade Science Content Standards: Investigation and Experimentation4. Scientific progress is made by asking meaningful questions and

conducting careful investigations. As a basis for understanding thisconcept and addressing the content in the other three strands, studentsshould develop their own questions and perform investigations.

F. Use magnifiers or microscopes to observe and draw descriptions ofsmall objects or small features of objects.G. Follow oral instructions for a scientific investigation.

Teachers: Geology The Study of the Changing EarthGeology is the study of planet Earth, its rocky exterior, its history, and theprocesses that act upon it. Not only do geologists seek to understand how theEarth formed and changed into what it is today, they also try to predict how ourplanet will behave. An important part of their studies is examining the recordsprovided by rocks.

A rock is a naturally occurring solid consisting of one or more minerals. Amineral is a naturally occurring solid that is not living. Rocks are everywhere: inthe ground, forming mountains, at the bottom of the oceans. Earths crust orouter layer is also made mostly of rock.

Depending on how they form, rocks are divided into three main types: igneous,sedimentary and metamorphic. Igneous rocks are the primary original materialthat makes up the Earths surface. Igneous rocks are made of old rocks thathave melted within the Earth to form molten material called magma. When it isexpelled from volcanoes onto the Earths surface, it is known as lava.

Eventually, magma cools, solidifies and crystallizes to become igneous rocks.This occurs either beneath the Earths surface or following an eruption of avolcano at the surface. Obsidian and granite are examples of igneous rocks.Rocks that come into contact with the atmosphere and with water are graduallyweathered, meaning that rocks are broken down into smaller pieces. Rain,wind, snow, and the freezing and thawing of water can all cause small bits ofrock to be worn down from a larger rock. Particles of weathered rock are carried

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away by wind or water and settle in different places, a process known aserosion. In the new location, layers of sediment are formed. Eventually thelayers of sediment harden and become compacted or cemented, through a

process called lithification, to form sedimentary rocks. Limestone andsandstone are examples of sedimentary rocks.

Metamorphic rocks are created when existing rocks are exposed to hightemperatures and pressures, and the rock is changed, ormetamorphosed toform a metamorphic rock. Almost all metamorphism occurs deep in youngmountain ranges as rocks are folded and compressed beneath other rocks, allthe while exposed to high temperature and pressure. Phyllite and slate areexamples of metamorphic rocks.

The rock cycle describes how rocks form and change from one type to another.

For example, any type of rock (igneous, sedimentary, or metamorphic) canbecome metamorphic if it is buried deep enough. Then, if the temperature andpressure become sufficiently high, the rock can melt to form magma and a newigneous rock. The rock cycle is a natural recycling process of Earth material.

Activity: The Rock Cycle

Materials:

Play Doh (3 colors, each rolled into a ball the size of a golf ball)

Food grater

Paper plate

Procedure:

Explain the rock cycle as you perform the different processes described below.Relate each process to a step in the rock cycle.

1. Roll 3 colors of Play Doh into individual balls approximately 1 indiameter. This will represent igneous rocks. Remind the students thatigneous rocks are formed from the cooling of magma.

2. Grate some of each of the igneous rocks to represent weathering.

3. Take each of the three colors of sediment and layer them one on top ofthe other. Gently compress one pile of each color on top of the other inorder to make a layered effect, while also showing the individual particles.This model will represent lithification and result in a sedimentary rock.

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4. Apply greater pressure to the model of the sedimentary rock to show theprocess of metamorphism. The final model will represent metamorphicrock.

Remind the students that the metamorphic rock can be weathered if it remainson the earths surface or can be melted into igneous rock if it becomes deeplyburied, becoming magma once again.