Our Changing Earth

Unit Review Sheet

Facts and Definitions

Lesson 1: The Rock Cycle

• The rock cycle is a process where rocks, over time, are changed into other types of rocks.
• Magma is liquid rock found deep inside the Earth.
• The rock cycle includes igneous rocks formed from magma, metamorphic rocks formed from pressure and heat, and sedimentary rocks formed from sediment or small bits of other rocks.
• We can see the changes in environments that are caused by the rock cycle, but most parts of the rock cycle itself are too slow for human beings to observe as they happen.
• Rocks are made of combinations of many different minerals.

Lesson 2: Inside the Earth

• The Earth is made up of 4 layers: inner core, outer core, mantle, and crust.
• The lithosphere describes the Earth's crust and the solid part of the upper mantle.
• The asthenosphere is the soft, thick, fluid part of the mantle.
• Plate tectonics is a scientific theory that describes the slow movement of the plates that make up the crust of the Earth.

Lesson 3: Igneous Rocks and Volcanoes

• Igneous rocks are rocks formed from magma, which includes molten, liquid minerals.
• Igneous rocks can be either intrusive — if they cool below the Earth's surface — or extrusive — if they cool on the Earth's surface.
• There are over 150 volcanoes in the United States.
• The three main types of volcanoes are cinder cone, shield, and composite cone.

Lesson 4: Earthquakes and Moving Plates

• Seismologists are scientists who study earthquakes.
• Plate boundaries are where tectonic plates meet, while faults are breaks in the Earth's crust where rocks can move past each other.
• The epicenter is the focus point of an earthquake on the Earth's surface.

Lesson 5: Metamorphic and Sedimentary Rocks

• Metamorphic rocks are created when rocks deep below the Earth's surface are exposed to extreme heat and/or pressure.
• Foliated metamorphic rocks are layered, meaning that sheets or bands are visible in the rock.
• Non-foliated metamorphic rocks do not have regular layers.
• Sedimentary rocks form when small bits of rock and other material get squeezed and glued together.
• Lithification is a process where loose bits of sediment are compacted (squeezed) and then cemented (glued) together to form sedimentary rocks.

Lesson 6: Weathering

• Weathering means breaking rocks down into smaller pieces through processes that are physical (wind, ice, etc.) or chemical (water mixing with chemicals to form acids that break down rocks).
• Biological weathering occurs when living things break down rocks. This type of weathering can be physical (tree roots growing into a rock) or chemical (mosses producing chemicals that dissolve rocks).
• Any type of rock — igneous, metamorphic or sedimentary — can be weathered.
• Soil is made up of a variety of things including mineral sediments from weathered rocks.

Lesson 7: Erosion

• When pieces of sediment weathered from rocks are moved from one place to another, it is called erosion.
• Erosion can be caused by wind, water, gravity, or a combination of these.
• When eroded sediments come to rest, it is called deposition.

Final Project: Presenting the Rock Cycle

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