In this passage, 'magma' refers to rock that is

melted into liquid (The text defines magma as rock that intense heat 'melts ... into a glowing liquid.')

According to the text, sedimentary rock forms when

grains settle and are pressed in layers (The passage says grains settle in layers and the weight above presses them into sedimentary rock.)

The best title for the central idea of this passage is

How Rocks Constantly Change Form (The passage describes the rock cycle, the endless loop in which rock changes form.)

Based on the passage, what would have to happen for a metamorphic rock to become igneous rock?

It would need to melt into magma and then cool (Igneous rock forms when magma cools, and the passage says rock that sinks far enough to melt "becomes magma again," so the metamorphic rock must melt first and then harden.)

How Rock Becomes Rock Again: Level 3 Reading Comprehension Questions

Rock may look permanent, but over long stretches of time it changes from one form into another. Deep below the surface, intense heat melts rock into a glowing liquid called magma. When magma cools, either underground or after erupting from a volcano, it hardens into igneous rock.

Wind and water then break that rock into tiny grains. The grains settle in layers at the bottom of lakes and seas, and over millions of years the weight above presses them into sedimentary rock.

If sedimentary rock is buried deeper still, heat and pressure can squeeze and bake it into metamorphic rock without fully melting it. Should that rock sink far enough to melt, it becomes magma again. Geologists call this endless loop the rock cycle, and it has been turning for billions of years.

Because each step takes so long, a single grain of sand may carry the history of several different rocks within it, a record patient observers can learn to read.

Comprehension questions