Category 1: Constructive or Destructive?
After a volcanic eruption, lava cools and hardens into rock. Over time, repeated eruptions create more land.
Question: What type of process is occurring?
Constructive process
A river flows quickly past its banks and carries pieces of sediment downstream.
Question: Which process is occurring?
Answer: Erosion
Grass grows beside a stream. Its roots hold the soil in place during rainstorms.
Question: How is the grass affecting erosion?
Answer: It reduces or prevents soil erosion.
Plants grow on a beach, and their roots hold sand in place. Over time, sand builds up around the plants.
Question: Which plants from the textbook are most likely responsible?
Answer: Sea oats
People build a barrier across a river to hold back water for irrigation and drinking.
Question: What structure did they build?
Answer: A dam
Strong winds and water slowly wear rock away from the side of a mountain. Over time, the mountain becomes lower.
Question: What type of process caused this change?
Destructive process
After carrying sediment downstream, a river slows as it reaches a larger body of water. The sediment falls to the bottom and begins piling up.
Question: Which process is occurring now?
Answer: Deposition
A tree begins growing in a crack in a rock. As its roots grow larger, pieces of rock break off.
Question: Is the tree having a constructive or destructive impact?
Answer: Destructive
A beach loses most of its sea oats. Strong winds begin blowing loose sand away instead of allowing it to build up.
Question: Which landform may have difficulty forming?
Answer: Sand dunes
A community near a river frequently floods. People construct a raised wall along the riverbank to keep water from reaching homes.
Question: What structure did they build?
Answer: A levee
Two land masses push together. Rocks and dirt rise, causing the land's elevation to increase.
Question: Which surface feature is most likely forming?
A mountain
For many years, a river carries sediment and drops it near the end of the river. Eventually, new land forms.
Question: What landform has most likely formed?
Answer: A delta
Beavers use trees, mud, and rocks to build a dam across a river. A wetland begins forming behind it.
Question: Why is this considered a constructive impact?
Answer: The beavers' dam creates a wetland/new habitat and slows water flow.
A farmer's crops are planted on a steep hill. Rainwater rushes downhill and washes away soil, seeds, and young plants. The farmer creates level steps along the hillside.
Question: What practice is the farmer using?
Answer: Terrace cultivation
A town clears a forest to construct roads, schools, homes, and stores. Animals that once lived there lose their habitat.
Question: Is this an example of a constructive or destructive environmental impact?
Answer: Destructive
Wind carries sand across an area. When the wind slows, the sand is deposited in mounds.
Question: What landform is being created, and is this constructive or destructive?
A sand dune; constructive
Maria says delta formation is destructive because the river first erodes sediment from its banks. James says delta formation is constructive because the sediment is eventually deposited and creates land.
Question: Whose conclusion best describes the formation of the delta?
Answer: James's; delta formation is constructive.
A fast-growing vine covers trees, buildings, and other plants. Native plants underneath it cannot receive what they need to survive.
Question: Which organism from the textbook is causing this destructive impact?
Answer: Kudzu
After the farmer creates level steps, rainwater moves more slowly and has time to soak into the ground.
Question: How does this practice help the land?
Answer: It manages water flow and reduces soil erosion.
A human-made dam controls water, but afterward fish have difficulty migrating and the river's natural course changes.
Question: What does this scenario demonstrate about human-made dams?
Answer: They can be helpful but can also have destructive impacts on the environment.
A student says, “Volcanoes are always destructive because lava can destroy everything in its path.” Another student disagrees because cooled lava can create new land.
Question: Which student has the stronger explanation?
Answer: The second student, because volcanoes can be both destructive and constructive.
A river rises after heavy rain and water moves onto nearby land, damaging homes and businesses.
Question: What event has occurred?
Answer: A flood
Gopher tortoises move seeds to new locations. The seeds eventually grow into plants.
Question: Is this impact constructive or destructive? Explain.
Constructive because the dispersed seeds can grow into new plants.
During a hurricane, ocean waves and storm surge move toward a coastal community. A large mound of sand covered with sea oats stands between the water and buildings.
Question: How can this surface feature help the community?
Answer: The sand dune acts as a natural barrier against storm surges, ocean waves, erosion, and flooding.
A levee protects one community from flooding. Farther downstream, however, flooding and erosion increase.
Question: What conclusion can be made from this evidence?
Answer: Levees can reduce flooding in one location but may increase flooding and erosion downstream.