Science · Level 3 · 162 words
How Rock Becomes Rock Again
Original passage © Team AM, written for Hone Literacy.
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
1. In this passage, 'magma' refers to rock that is
- A frozen solid
- B melted into liquid
- C broken into grains
- D pressed into layers
Show answer
B. melted into liquid
The text defines magma as rock that intense heat 'melts ... into a glowing liquid.'
2. According to the text, sedimentary rock forms when
- A magma cools quickly
- B grains settle and are pressed in layers
- C rock melts underground
- D volcanoes erupt
Show answer
B. grains settle and are pressed in layers
The passage says grains settle in layers and the weight above presses them into sedimentary rock.
3. The best title for the central idea of this passage is
- A Volcanoes Around the World
- B How Rocks Constantly Change Form
- C Why Lakes Form Layers
- D The Work of Geologists
Show answer
B. How Rocks Constantly Change Form
The passage describes the rock cycle, the endless loop in which rock changes form.
Source: Written for Hone Literacy. Original passage © Team AM, written for Hone Literacy.