All practice questions

### Models of Snowball Earth Initiation

Geological evidence suggests that during the Neoproterozoic era, Earth experienced global glaciations where ice sheets reached the equator (the "Snowball Earth" hypothesis). Two models propose different mechanisms for how this extreme cooling was initiated.

Model 1 (Volcanic Aerosol Albedo)
This model proposes that a series of massive, low-latitude volcanic eruptions released vast quantities of sulfur dioxide ($SO_2$) gas into the stratosphere. In the stratosphere, $SO_2$ reacted with water vapor to form highly reflective sulfate aerosols. These aerosols remained suspended for years, reflecting incoming solar radiation back into space. The resulting surface cooling initiated the expansion of polar ice caps. Because ice has a high albedo (reflectivity), the expanding ice reflected even more sunlight, creating a runaway ice-albedo feedback loop that rapidly froze the entire planet. The primary driver was thus the reduction in absorbed solar energy due to stratospheric aerosols.

Model 2 (Silicate Weathering Drawdown)
This model proposes that the breakup of the supercontinent Rodinia, which was positioned near the equator, initiated global glaciation. Because the continents were in a warm, wet equatorial region, weathering of silicate rocks occurred at extremely high rates. The chemical weathering of silicate rocks removes carbon dioxide ($CO_2$) from the atmosphere and sequesters it in ocean sediments. The rapid continental breakup also increased runoff, accelerating this process. The depletion of atmospheric $CO_2$ weakened the greenhouse effect, causing global temperatures to plummet. Once temperatures dropped sufficiently, polar ice caps began to expand, initiating the ice-albedo feedback loop. The primary driver was thus the reduction in atmospheric greenhouse gas concentrations.

Based on the descriptions of Model 1 and Model 2, match each statement about the initiation of Snowball Earth to the model or models it represents.

The unique hunting strategy of the archerfish has long fascinated marine biologists. Operating in the brackish waters of mangrove swamps, this remarkable predator, in order to capture prey, shoots a jet of water from its mouth to knock insects off overhanging branches. The force of these aquatic projectiles, in addition to the fish's highly specialized eyesight, allow it to target and hit insects with remarkable precision from several feet away.

Which of the following options is the correct form of the underlined verb to complete the sentence?

To write a successful grant proposal, a scientist must state the research goals clearly, provide a detailed budget, and a realistic timeline should be outlined. This thorough preparation increases the likelihood of securing funding. Ultimately, a well-crafted proposal convinces reviewers of the project's viability. Which choice best completes the sentence while maintaining a consistent grammatical construction?

Architectural historians have noted that the intricate geometric carvings decorating the palace walls are characteristic to the late Islamic style, which emphasized complex ornamentation over pictorial representation. Which choice best replaces the underlined portion of the sentence?

Read the sentence below. Which present-tense form of the verb 'to provide' correctly completes the sentence to maintain proper subject-verb agreement?

Aerogel is composed of up to 99.8 percent air, giving it a delicate, ghost-like appearance. [1] _As a result, it_ is remarkably durable and can withstand significant pressure.

Which choice provides the most logical transition from the preceding sentence?

During the late nineteenth century, the expansion of the transcontinental railroad transformed the American West, it allowed goods to be shipped across the country in days rather than months. Consequently, remote towns grew into bustling economic hubs almost overnight, attracting merchants and laborers alike. This rapid industrialization, however, also brought significant environmental challenges to the region.

Which of the following choices best corrects the underlined portion?

Originally constructed during the Gilded Age, the grand library serves as a testament to early twentieth-century civic architecture. Its soaring vaulted ceilings and ornate marble columns evoke a sense of scholarly reverence. Consequently, visitors are expected to chill out and be quiet in the main reading room.

Which of the following choices best maintains the tone established in the passage?

Fill in the blank with the correct phrase from the brackets to complete the sentence without creating a dangling modifier:

[the cartographer noticed several topographical errors / several topographical errors were noticed by the cartographer]

### The Source of the Earth's Hum

Earth is constantly vibrating at extremely low frequencies, a phenomenon known as the "microseismic hum." This hum persists even in the absence of earthquakes. Two scientists present competing hypotheses regarding the primary source of this hum.

Scientist 1
The Earth's hum is driven entirely by ocean wave interactions. When ocean waves of similar frequencies travel in opposite directions, they collide. This collision generates standing pressure waves that do not decay with depth. These pressure waves propagate through the water column and strike the seafloor, generating seismic waves (oceanic microseisms) that travel through the Earth's crust. Because ocean wave activity is continuous and global, this mechanism accounts for the uninterrupted nature of the Earth's hum.

Scientist 2
The hum is caused by atmospheric dynamics, not oceanic activity. Turbulence in the atmosphere, wind shear, and atmospheric gravity waves exert varying vertical pressures directly on the continents. These atmospheric pressure fluctuations couple with the solid Earth, transferring acoustic energy directly into the crust. The hum is most intense over landmasses where atmospheric storm systems are active, demonstrating that the primary driver is atmospheric force rather than deep-ocean wave interactions.

Which of the following statements best summarizes Scientist 2's central hypothesis regarding the origin of the Earth's hum?

Scientists analyzing Antarctic ice cores can reconstruct the Earth's climate history over hundreds of thousands of years. By measuring the concentration of greenhouse gases trapped in tiny air bubbles, researchers gather crucial data about ancient atmospheric conditions. These chemical signatures give us the lowdown on how past climate shifts correlate with global temperature changes.

Which choice best maintains the established tone of the passage?

Read the sentence below:

Although the archaeologist claimed to have discovered the ruins of an ancient city, she could not find any physical evidence to collaborate her theory.

Which of the following options is the correct word to replace the underlined portion of the sentence?

Which pronoun correctly fills the blank to ensure that the passage maintains a consistent third-person plural perspective and avoids a shift in pronoun person?

The following sentence contains an underlined portion:

'Although Venus and Mars are both terrestrial planets with rocky compositions, Venus possesses a much denser atmosphere than that of Mars, which traps heat and creates surface temperatures hot enough to melt lead.'

Which choice best completes the sentence grammatically?

During the deep-sea expedition, the chief oceanographer instructed the research assistant and she to verify they're salinity data before publishing the report.

Which of the following is the correct form of the underlined portion of the sentence?

By utilizing advanced sonar mapping, the sunken vessel's exact location was identified by the marine historians in the deep waters of the Atlantic.

Which choice most logically and grammatically completes the sentence?

In the passage below, a portion of the text is underlined.

Although humpback whales are known for their complex songs, their migration patterns are equally fascinating to marine biologists. These researchers use satellite tags to track the whales across vast ocean basins. During the winter, humpback whales gather in warm tropical waters to breed, however, they do not feed again until they return to polar regions in the spring. This annual journey is one of the longest migrations of any mammal on Earth.

Which of the following options is the best replacement for the underlined portion?

A community library has a collection of 250 books. If $44\%$ of these books are classified as fiction, how many fiction books are in the library's collection?

To prepare for the upcoming solar eclipse, astronomers calibrated the sensitive, modern telescopes, that had been installed on the summit of Mauna Kea. Which choice is the best version of the underlined portion of the sentence?

Having spent millions of years buried under layers of volcanic ash, the paleobotanist easily identified the fossilized leaf as an extinct species of fern.

Which of the following choices best restores grammatical correctness to the underlined portion of the sentence?