1. Magma that has cooled and solidified on Earth’s surface is best described as which of the following?
A. Clay
B. Iron ore
C. Igneous rock Correct
D. Volcanic ash
Explanation
Magma is molten rock. When it cools and solidifies on the Earth's surface (extrusive), it forms igneous rock (e.g., basalt, rhyolite). Volcanic ash (D) is fragmented material ejected during an eruption, not solidified magma. Clay (A) and iron ore (B) are sedimentary/metamorphic materials.
2. How long does it take the Earth to complete one revolution around the Sun?
A. One day
B. One week
C. One month
D. One year Correct
Explanation
One revolution around the Sun defines a year (approximately 365.25 days). One day (A) is one rotation on Earth's axis.
3. Which THREE of the following processes depend directly on solar energy?
A. Seafloor spreading
B. The water cycle Correct
C. Photosynthesis Correct
D. Atmospheric circulation Correct
Explanation
The water cycle (evaporation, transpiration), photosynthesis (light energy), and atmospheric circulation (heating differences) are all directly driven by solar energy. Seafloor spreading is driven by internal geothermal heat from Earth's mantle.
4. Which of the following layers of Earth is the most dense?
A. The inner core Correct
B. The mantle
C. The oceanic crust
D. The continental crust
Explanation
Density increases toward Earth's center. The inner core is composed of solid iron and nickel and is the densest layer. The mantle is less dense, and crust (oceanic and continental) is the least dense.
5. Which of the following is the most abundant gas in Earth’s atmosphere?
A. Hydrogen
B. Nitrogen Correct
C. Helium
D. Methane
Explanation
Nitrogen (N₂) makes up about 78% of Earth's atmosphere by volume. Oxygen is second at about 21%. The other gases listed are trace constituents.