ICAS - ICAS Earth and Environmental Science Questions and Answers — Questions and Answers
Question 1: A community notices that a nearby river, which was once clear, has become murky and has less fish. A new factory opened upstream last year. Local authorities find high levels of nitrates and phosphates in the water near the factory's discharge pipe. What is the most likely immediate consequence of this type of pollution?
- An increase in water temperature, killing off sensitive fish species.
- The water becoming more acidic, dissolving the shells of aquatic organisms.
- A rapid growth of algae, which then die and decompose, depleting oxygen. (Correct answer)
- Heavy metals accumulating in the riverbed, poisoning bottom-dwellers.
Correct answer: A rapid growth of algae, which then die and decompose, depleting oxygen.
High levels of nitrates and phosphates are nutrients that cause eutrophication. This process leads to a rapid increase in algae population, known as an algal bloom. When these algae die, decomposers like bacteria break them down, a process that consumes large amounts of dissolved oxygen in the water. This deoxygenation can lead to fish kills and create a 'dead zone'.
Question 2: Which of the following best describes the mechanism that drives the movement of Earth's tectonic plates?
- The gravitational pull of the Moon and Sun on the Earth's crust.
- Convection currents in the molten mantle beneath the lithosphere. (Correct answer)
- The spinning of the Earth on its axis, causing the plates to shift.
- The expansion and contraction of the crust due to solar heating and cooling.
Correct answer: Convection currents in the molten mantle beneath the lithosphere.
The primary driving force for plate tectonics is the slow movement of hot, less dense rock rising and cooler, denser rock sinking within the Earth's mantle. These circular convection currents exert a powerful force on the overlying lithospheric plates, causing them to move, collide, separate, and slide past each other.
Question 3: Deforestation for agriculture and urban development is a major environmental concern. Which of the following is a direct consequence of large-scale deforestation?
- A decrease in average global sea level.
- An increase in soil quality and fertility.
- A decrease in the amount of carbon dioxide in the atmosphere.
- An increase in soil erosion and downstream sedimentation. (Correct answer)
Correct answer: An increase in soil erosion and downstream sedimentation.
Tree roots are crucial for holding soil in place. When forests are cleared, the soil is left exposed to wind and rain, leading to increased rates of erosion. This eroded soil is then transported into rivers and streams, causing sedimentation which can harm aquatic ecosystems and affect water quality.
Question 4: The carbon cycle is the process by which carbon is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere. Human activities have significantly altered this cycle. Which human activity is the primary contributor to the increase of carbon dioxide in the atmosphere?
- The use of nitrogen-based fertilizers in agriculture.
- The burning of fossil fuels for energy. (Correct answer)
- Large-scale commercial fishing operations.
- The disposal of plastic waste in landfills.
Correct answer: The burning of fossil fuels for energy.
Fossil fuels like coal, oil, and natural gas are ancient carbon stores. When humans burn them for electricity, transportation, and industry, this stored carbon is released into the atmosphere as carbon dioxide (CO2), a potent greenhouse gas. This is the main driver of the observed increase in atmospheric CO2 concentrations.
Question 5: A geologist is studying a region and finds a long mountain range with active volcanoes and frequent, deep earthquakes. The oceanic crust on one side of the mountain range is significantly younger than the continental crust on the other. What type of plate boundary is this geologist most likely studying?
- Divergent boundary
- Convergent boundary (oceanic-continental subduction) (Correct answer)
- Transform boundary
- Convergent boundary (continental-continental collision)
Correct answer: Convergent boundary (oceanic-continental subduction)
The features described—a volcanic mountain range on a continent, deep earthquakes, and an age difference between oceanic and continental crust—are all characteristic of an oceanic-continental subduction zone. Here, the denser oceanic plate sinks (subducts) beneath the less dense continental plate, melting and creating magma that feeds volcanoes, while the friction and stress cause deep earthquakes.
Question 6: Which of the following correctly describes a sequence in the rock cycle?
- Igneous rock undergoes weathering and erosion to form sediment, which is then compacted and cemented to form sedimentary rock. (Correct answer)
- Metamorphic rock melts to form magma, which then cools and solidifies to form sediment.
- Sedimentary rock is exposed to intense heat and pressure, causing it to erode into metamorphic rock.
- Magma crystallizes to form sedimentary rock, which is then weathered to form igneous rock.
Correct answer: Igneous rock undergoes weathering and erosion to form sediment, which is then compacted and cemented to form sedimentary rock.
The rock cycle describes the transformations between the three main rock types. A key pathway is when any rock type (including igneous) is exposed at the surface, it breaks down through weathering and erosion. The resulting particles (sediment) are transported and deposited. Over time, the accumulated sediment is buried, compacted, and cemented together to form sedimentary rock.
ICAS - ICAS Earth and Environmental Science Questions and Answers
A community notices that a nearby river, which was once clear, has become murky and has less fish.
A new factory opened upstream last year.
Local authorities find high levels of nitrates and phosphates in the water near the factory's discharge pipe.
What is the most likely immediate consequence of this type of pollution?