Carving the Earth: Lake Basin Formation Quiz

If a massive ice sheet moves across the land, then it carves deep depressions into the crust; if those glaciers then melt and fill the depressions with water, then a glacial lake basin is formed.

If tectonic plates move away from each other, then the Earth's crust stretches and thins; if the crust eventually breaks and drops down, then a deep valley or basin is created that can collect water.

If a large magma chamber beneath a volcano empties during an eruption, then the overhead mountain loses its support; if the summit subsequently collapses inward, then a large circular depression called a caldera is formed.

If a river meanders across a flat plain, then erosion and deposition can eventually cut off a loop from the main channel; if this loop becomes isolated, then an oxbow lake is formed.

If a retreating glacier leaves behind a large block of buried ice, then a hole remains after the ice melts; if this hole fills with groundwater or rainwater, then it is known as a kettle lake.

If groundwater dissolves soluble bedrock like limestone over time, then underground cavities form; if the roof of such a cavity collapses, then a sinkhole is created that may fill with water to become a lake.

If a massive amount of rock and debris falls into a narrow valley, then it can block the flow of a river; if the water is trapped behind this natural dam, then a lake basin is created.

If tectonic plate movements isolate a portion of the ocean from the global sea system, then that water body becomes a landlocked basin; if it is surrounded by land, then it is classified as a lake.

If a glacier carves a bowl-shaped depression (cirque) high in a mountain, then it leaves a basin behind; if that basin fills with water after the glacier retreats, then it is called a tarn.

If tectonic stress causes the lithosphere to fracture and pull away, then a rift valley forms; if water fills this valley, then it is the result of the rifting process.

If an explosion or impact occurs, then a crater is blasted out; if a volcano's support system collapses, then a caldera is formed, meaning the primary distinction is the method of basin creation.

If a lake basin exists, then it acts as a trap for clay, silt, and organic matter; if these materials accumulate over thousands of years, then the lake will eventually fill in and disappear.

If glacial lakes require the movement and melting of ice to form, then they must occur where glaciers were present; if glaciers are restricted to cold climates, then these lakes appear in high latitudes or altitudes.

If a living organism modifies the environment to trap water, then the basin has a biological origin; if the origin is biological, then it is classified as an organic or biogenic lake.

If a celestial body hits the Earth at high speed, then it creates a circular depression; if the intense heat and pressure alter the surrounding rocks, then shocked minerals will be present in that basin.

If tectonic rifting creates deep fractures in the Earth's crust, then the resulting basins are often extremely deep; if glaciers only scour the surface, then tectonic lakes (like Lake Baikal) are typically much deeper.

If we measure how much of the Earth's surface is altered by a process, then we are determining the spatial scale; if a glacier covers a continent, the scale is large, whereas a single sinkhole is a small spatial scale.

If a river carries sediment to the ocean or a larger lake, then it builds a delta; if the shifting sediment blocks off a body of water, then a deltaic lake is formed.

If pre-existing valleys are aligned with the flow of a massive ice sheet, then the ice will deeply scour those valleys; if the ice retreats and leaves behind deep troughs, then those troughs become long, narrow glacial lakes.

If rifting depends on the slow movement of tectonic plates, then it takes millions of years; if a landslide is a sudden mass wasting event, then the lake basin is created almost instantly.