Soal Latihan dan Jawaban Reading Comprehension 05
In Death Valley, California, one of the hottest, most arid places in North America, there is
much salt, and salt can damage rocks impressively. Inhabitants of areas elsewhere, where
streets and highways are salted to control ice, are familiar with the resulting rust and
deterioration on cars. That attests to the chemically corrosive nature of salt, but it is not
(5) the way salt destroys rocks. Salt breaks rocks apart principally by a process called crystal
prying and wedging. This happens not by soaking the rocks in salt water, but by moistening
their bottoms with salt water. Such conditions exist in many areas along the eastern edge
of central Death Valley. There, salty water rises from the groundwater table by capillary
action through tiny spaces in sediment until it reaches the surface.
(10) Most stones have capillary passages that suck salt water from the wet ground. Death
Valley provides an ultra-dry atmosphere and high daily temperatures, which promote
evaporation and the formation of salt crystals along the cracks or other openings within
stones. These crystals grow as long as salt water is available. Like tree roots breaking up a
sidewalk, the growing crystals exert pressure on the rock and eventually pry the rock apart
(15) along planes of weakness, such as banding in metamorphic rocks, bedding in sedimentary
rocks, or preexisting or incipient fractions, and along boundaries between individual
mineral crystals or grains. Besides crystal growth, the expansion of halite crystals (the same
as everyday table salt) by heating and of sulfates and similar salts by hydration can
contribute additional stresses. A rock durable enough to have withstood natural conditions
(20) for a very long time in other areas could probably be shattered into small pieces by salt
weathering within a few generations.
The dominant salt in Death Valley is halite, or sodium chloride, but other salts, mostly
carbonates and sulfates, also cause prying and wedging, as does ordinary ice. Weathering
by a variety of salts, though often subtle, is a worldwide phenomenon. Not restricted to
(25) arid regions, intense salt weathering occurs mostly in salt-rich places like the seashore,
near the large saline lakes in the Dry Valleys of Antarctica, and in desert sections of
Australia, New Zealand, and central Asia.
Reading Comprehension 05
The impressive salt rocks in Death Valley.
The destructive effects of salt on rocks.
The damaging effects of salt on roads and highways.
The amount of salt produced in Death Valley.
They both react quickly to a rise in temperature.
They both grow as long as water is available.
They both force hard surfaces to crack.
They both cause salty water to rise from the groundwater table.
simplify the explanation of crystal prying and wedging
explain how some rocks are not affected by salt
present an alternative theory about crystal growth
introduce additional means by which crystals destroy rocks
Salts usually cause damage only in combination with ice.
Only two types of salts cause prying and wedging.
A variety of salts in all kinds of environments can cause weathering.
Salt damage at the seashore is more severe than salt damage in Death Valley.
They show similar kinds of damage as rocks in Death Valley.
They do not allow capillary action of water.
They contain more carbonates than sulfates.
They are protected from weathering.