AP Environmental Science Unit 4 Practice Test: Earth Systems & Resources

The correct answer is (B). Beneath the ocean floor, tectonic plates move away from each other at the divergent plate boundary. A subduction zone is where the tectonic plates pass over one another. Seafloor spreading does not describe the movement of the plates; instead, it describes the mantle pushing upward through to the surface. At a convergent plate boundary, the tectonic plates move toward one another, and at a transform fault boundary, the plates move past each other. The tectonic plates move away from each other due to the force of magma rising through and splitting the lithosphere, of which the tectonic plates are made.

The correct answer is (B). The inner and outer core of the earth both consist of iron and nickel. Although the inner core is hot, its accompanying 330–360 gigapascal pressure keeps it in the solid phase. The outer core, although hot, lacks the pressure to keep it in the solid phase; consequently, it is the only layer of Earth in the liquid phase. The mantle is made up of magma, which is molten rock, and not considered liquid. The asthenosphere is semi-molten, but not liquid. The lithosphere is composed of both the earth’s crust and the outer mantle, both of which are solid.

The correct answer is (B). Soil degradation describes the loss of some or all of a soil’s ability to support plant growth resulting from biological, chemical, or physical deterioration. Weathering describes the breakdown of rocks and minerals, not soil. Erosion describes the process by which rock fragments and soils are removed from a landscape, but does not specifically describe a soil’s capacity for supporting plant growth. Base saturation describes the proportion of soil bases to soil acids, and does not specifically relate to soil supported plant growth.

The correct answer is (B). As soil ages, the amount of organic material in it increases proportionally. Immature soil develops into young soil as plants and organisms die. Eventually, young soil becomes mature soil, which contains all of organic material present in each of the earlier stages.

The correct answer is (B). The troposphere is the lowest portion of the atmosphere and ranges in depth from about 8 km – 14.5 km. The stratosphere is the second layer of the atmosphere and contains the ozone layer. The third layer, the mesosphere, is where most meteors burn up when entering the atmosphere. The thermosphere is the fourth layer and is where the International Space Station orbits.

The correct answer is (A). The innermost layer of the earth is the solid inner core, followed by the liquid outer core, then the mantle and finally the crust.

The correct answer is (D). Transform plate boundaries occur when plates move sideways past each other.

The correct answer is (C). The B horizon consists mostly of minerals and very little organic matter.

The correct answer is (A). A soil’s texture is determined by the percentages of sand, silt and clay contained in the soil.

The correct answer is (D). No more than 3% of Earth’s water is fresh water. Fresh water sources are approximately distributed as follows:

0.04% Atmospheric water
0.3% Surface water
30% Ground water
68+% Ice and glaciers

The correct answer is (B). The following lists the atmospheric layer from the closest to the Earth increasing in altitude:

Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere