CELPIP Reading Part 3 Practice Test: How Limestone Caves Form And Change

Paragraph A

Most limestone caves begin when slightly acidic water enlarges existing weaknesses in soluble rock. Rain absorbs carbon dioxide from the air and especially from soil, forming weak carbonic acid. As the water follows fractures, joints, and bedding planes, it dissolves small amounts of calcite and gradually widens connected passages. The process commonly occurs below the water table, although later drainage may expose the resulting spaces to air. A mapped cave is only the humanly accessible part of a larger groundwater system; water can travel through cracks too narrow for explorers. Passage size therefore gives an incomplete picture of where dissolution is occurring. Together, the separate details explain the wider pattern while showing why no single observation can represent the whole.

Paragraph B

Cave levels often reflect changes in surrounding drainage. If a river cuts its valley deeper, the local water table may fall, leaving an upper passage dry while dissolution continues along a new lower route. Several horizontal levels can thus record successive stages of valley development rather than simultaneous excavation. Water may also abandon one route after sediment blocks it or a shorter connection opens. Because underground drainage crosses beneath surface divides, the stream directly above a passage need not be the water that formed it. Tracing dyes and measuring flow are often required to determine which sinkholes, springs, and caves belong to the same system. The evidence therefore supports a connected interpretation without reducing the subject to one determining factor.

Paragraph C

Once a passage contains air, dripping water can deposit some of the calcite it previously dissolved. Carbon dioxide escapes from the water, reducing its ability to hold the mineral. Deposits growing downward from ceilings are stalactites, while those building upward from floors are stalagmites; sheets over walls or slopes are called flowstone. Growth rates vary sharply with water supply, chemistry, temperature, and ventilation, so size alone is not a reliable clock. Many formations develop over long periods but can be broken by a single touch or impact. Even unbroken surfaces may be stained by mud or skin oils. Protected routes help keep visitors at a distance. Viewed together, the evidence connects immediate observations with the broader pattern they collectively produce.

Paragraph D

Caves preserve fossils, mineral layers, sediments, and biological communities that can reveal past environments and long isolation. Their stable darkness also supports organisms with specialized senses and low energy demands. Tourism can fund protection and public education, yet lights, paved paths, heat, and repeated visitors alter cave conditions. Artificial lighting may encourage algae near lamps, while traffic can change humidity or disturb animals. Managers use restricted routes, timed entry, low-heat lighting, and cleaning protocols to reduce these effects. Such controls limit harm but cannot make a developed cave identical to an undisturbed one, so sensitive chambers may remain closed. Researchers may also limit sampling frequency. The relationship becomes visible only when the separate conditions and their effects are read together.

Paragraph E

Not given in any of the above paragraphs.