Which statement best expresses the main idea?

Glaciers form from packed snow, cut the land with the rock they carry, and leave marks that outlast the ice itself. (The three paragraphs are formation, erosion, and evidence. Only one choice covers all three, and the passage directly contradicts the others.)

According to the passage, what shape is the floor of an old glacial valley?

a broad U (The passage contrasts the two: the glacial valley is broad and U-shaped, while a river valley narrows to a V.)

A geologist finds a large boulder in a flat field, hundreds of kilometres from the only mountain made of that rock. What does the passage best support?

Ice once crossed this land and brought the boulder from that mountain. (The last paragraph describes exactly this case: far-travelled boulders whose minerals identify the mountain, left behind by ice that has since melted.)

In this passage, "bedrock" means

the solid rock lying underneath the loose surface material (Stones in the base of the glacier scratch lines into the bedrock beneath, so it is the firm rock under the ice and the loose material.)

What the Ice Leaves Behind: Level 4 Reading Comprehension Questions

A glacier is snow that never had a summer. Where more falls in winter than melts in the warm months, the layers press down on one another until the air is squeezed out and the pile turns to ice. Once the ice is thick enough, its own weight makes it move, and a mass that looks perfectly still is in fact travelling downhill.

Its power comes from what it carries. Stones frozen into the base act like the teeth of a file, scratching parallel lines into the bedrock beneath. Meltwater seeps into cracks, freezes, expands, and prises whole blocks free, which the ice then carries away. Working together, these two actions widen a valley as well as deepen it, which is why an old glacial valley has a broad, U-shaped floor while a river valley narrows to a V.

The evidence outlasts the ice by a very long time. Ridges of mixed rubble mark where the edge of a glacier once stood. Boulders sit in open fields hundreds of kilometres from the mountain they were broken from, and the minerals in them tell geologists which mountain that was. Long after the last of the ice is gone, the land keeps a record of where it went and how far.

Comprehension questions