GED Science Earth's Resources, Cycles, and Natural Hazards Summary

Coal formed over millions of years from buried plant remains. Once we use it, it cannot be replaced in a human lifetime, so it is nonrenewable.

Wrong choices

• Trees: Trees can be replanted and regrow in a human lifetime, so they are renewable.
• Sunlight: Sunlight keeps arriving every day, so it is renewable.
• Wind: Wind keeps blowing, so it is renewable.

In the carbon cycle, plants and algae take carbon dioxide out of the air during photosynthesis and store the carbon in sugars. Burning fuels, respiration, and volcanoes return carbon dioxide to the air.

Wrong choices

• Burning fossil fuels: Burning fossil fuels adds carbon dioxide to the air.
• Animal respiration: Animals breathe out carbon dioxide, so respiration adds it to the air.
• Volcanic eruptions: Volcanoes release carbon dioxide into the air.

Mitigation means reducing the harm a natural hazard can cause. Raising homes above flood levels and building them to resist strong winds lowers damage from storm surge and wind.

Wrong choices

• Paving over coastal wetlands for parking lots: Wetlands soak up storm water and slow waves. Paving them makes flooding worse.
• Building homes as close to the water as possible: Homes closest to the water face the worst flooding and waves.
• Removing sand dunes to improve the ocean view: Sand dunes act as a barrier against storm waves. Removing them increases damage.

The Sun heats ocean water, and some of it turns into water vapor that rises into the air. This is evaporation. The vapor later cools and condenses into clouds, then falls as precipitation.

Wrong choices

• Runoff: Runoff is water flowing over land into streams and oceans.
• Infiltration: Infiltration is water soaking into the ground.
• Precipitation: Precipitation is water falling from clouds as rain or snow, the opposite direction.

Fossil fuels formed when the remains of plants and tiny sea organisms were buried deep underground. Over millions of years, heat and pressure changed them into coal, oil, and natural gas. Burning them releases the energy that the ancient organisms got from the Sun.

Wrong choices

• trash buried in landfills over the last 100 years: Fossil fuels took millions of years to form, far longer than any landfill has existed.
• salt left behind when ocean water evaporated: Evaporated seawater leaves salt deposits, not fuels.
• lava that cooled after volcanic eruptions: Cooled lava forms igneous rock, not fossil fuels.

As the magnitude rises from 3 to 6, the yearly count falls from 1,200 to 1. So strong earthquakes are much rarer than weak ones in this region.

Wrong choices

• Most earthquakes in the region are magnitude 6.: Only about 1 earthquake per year is magnitude 6, the fewest of all.
• The number of earthquakes goes up as the magnitude goes up.: The counts go down, not up, as the magnitude goes up.
• A magnitude 6 earthquake will happen in this region every year from now on.: These are averages from the past. They cannot promise an exact number in every future year.

Using a resource sustainably means meeting today's needs without using it up for the future. If the town pumps no more than the rain puts back each year, the aquifer will not run dry.

Wrong choices

• Pump extra water in dry years to keep use steady: In dry years, less rain refills the aquifer. Pumping more then would lower the water level.
• Pump as much water as possible while it lasts: Pumping as much as possible would use the water faster than it is replaced.
• Pave over the land above the aquifer to keep it clean: Paving stops rain from soaking into the ground, so the aquifer would refill even more slowly.

Plants cannot use nitrogen gas directly. Soil bacteria change it into forms plants can absorb. Animals get nitrogen by eating plants, and decomposers return it to the soil. This loop is the nitrogen cycle.

Wrong choices

• The rock cycle: The rock cycle describes how rocks change from one type to another.
• The carbon cycle: The carbon cycle moves carbon, not nitrogen, through living things and the air.
• The water cycle: The water cycle moves water through evaporation and precipitation.

1. Feet left to rise: 16 − 12 = 4 feet.
2. Time = 4 ÷ 0.5 = 8 hours.

Check: 0.5 × 8 = 4 feet, and 12 + 4 = 16 feet.

Wrong choices

• 4 hours: 4 is the number of feet left to rise, not the number of hours.
• 32 hours: 32 comes from 16 ÷ 0.5, using the full 16 feet instead of the 4 feet still to go.
• 2 hours: 2 hours of rising at 0.5 feet per hour would add only 1 foot.

Renewable resources such as sunlight, wind, and water are replaced naturally in a short time. Nonrenewable resources such as coal, oil, and natural gas formed over millions of years and exist in limited amounts.

Wrong choices

• Nonrenewable resources can never be used up.: Nonrenewable resources are limited, so they can be used up.
• Renewable resources never cause any harm to the environment.: Renewable sources can still have impacts. For example, dams change rivers and fish habitats.
• Nonrenewable resources are replaced by nature in a short time; renewable resources take millions of years to form.: This is reversed. Fossil fuels (nonrenewable) took millions of years to form.