Reading: Matching Headings: Question 1

A When lightning strikes ordinary sand, it can leave behind a strange souvenir: a hollow, glassy tube called a fulgurite. The name comes from the Latin word fulgur, meaning "lightning," and the object is sometimes nicknamed "petrified lightning" because its branching, root-like shape traces the exact path the electrical discharge took as it burrowed into the ground.

B A fulgurite forms almost instantly. A lightning bolt can heat the sand it touches to more than 1,800 degrees Celsius for a fraction of a second, hot enough to melt silica grains into liquid glass. As the current forces its way downward through the loose sand, it fuses a narrow channel of glass around itself; within moments the surrounding sand cools the melted material again, leaving a rigid, usually hollow tube where the bolt once passed.

C Fulgurites have been recovered from sandy environments on every continent except Antarctica, including desert dune fields in North Africa, beaches along the Atlantic coast of the United States, and even high, exposed mountain summits where storms are frequent. The largest specimens, found largely intact in loose desert sand, can extend more than two metres beneath the surface, branching downward in a shape that mirrors the lightning's search for the easiest route to the water table.

D Because a fulgurite forms in the exact spot and instant a lightning strike occurred, geologists treat well-preserved specimens as a kind of frozen record. By studying where fulgurites cluster and how deep they reach, researchers can estimate how often a region has been struck by lightning over long periods, and the fused sand itself can reveal what minerals were present in the ground at the moment of formation, sometimes centuries or millennia ago.

E Turning this record into usable data is not straightforward. Fulgurites are extremely brittle and often shatter the moment a shovel disturbs the surrounding sand, so researchers usually reinforce a specimen with plaster or resin before attempting to lift it. Collecting fulgurites is also banned within many national parks and protected reserves, meaning scientists frequently must negotiate special permits, further slowing the pace at which new specimens can be studied.

The passage has five paragraphs, A–E.

List of Headings i. What a fulgurite is and how it got its name ii. The chemistry of glass-making in modern industry iii. The instant physical process that turns sand into glass iv. A growing market for lightning-glass jewellery v. Where fulgurites have been discovered around the world vi. A frozen record of ancient storms and soil minerals vii. Using satellite data to predict future lightning strikes viii. The practical difficulties of excavating a fragile specimen

Choose the correct heading for each paragraph from the list of headings below.

Paragraph A Paragraph B Paragraph C Paragraph D Paragraph E