Soal Latihan dan Jawaban Reading Comprehension 71
A snowfall consists of myriads of minute ice crystals that fall to the ground in the
form of frozen precipitation. The formation of snow begins with these ice crystals in
the subfreezing strata of the middle and upper atmosphere when there is an adequate
supply of moisture present. At the core of every ice crystal is a minuscule nucleus, a
(5) solid particle of matter around which moisture condenses and freezes. Liquid water
droplets flouting in the supermodel atmosphere and free ice crystals cannot coexist
within the same cloud, since the vapor pressure of ice is less than that of water. This
enables the ice crystals to rob the liquid droplets of their moisture and grow continuously.
The process can be very rapid, quickly creating sizable ice crystals, some of which
(10) adhere to each other to create a cluster of ice crystals or a snowflake. Simple flakes
possess a variety of beautiful forms, usually hexagonal, though the symmetrical shapes
reproduced in most microscope photography of snowflakes are not usually found in
actual snowfall. Typically, snowflakes in actual snowfalls consist of broken fragments
and clusters of adhering ice crystals.
(15) For a snowfall to continue once it starts, there must be a constant inflow of moisture
to supply the nuclei. This moisture is supplied by the passage of an airstream over a
water surface and its subsequent lifting to higher regions of the atmosphere. The Pacific
Ocean is the source of moisture for most snowfalls west of the Rocky Mountains, while
the Gulf of Mexico and the Atlantic Ocean feed water vapor into the air currents over
(20) the central and eastern sections of the United States. Other geographical features also
can be the source of moisture for some snowstorms. For example, areas adjacent to the
Great Lakes experience their own unique lake-effect storms, employing a variation of
the process on a local scale. In addition, mountainous sections or rising terrain can
initiate snowfalls by the geographical lifting of a moist airstream.
Reading Comprehension 71
Why are snowflakes hexagonal?
In which months does most snow fall?
What is the optimum temperature for snow?
How are snowflakes formed?
A small snowflake
A drop of water
How ice crystals form
How moisture affects temperature
What happens when ice crystals melt
Where the moisture to supply the nuclei comes from
A decrease in the number of snowflakes
A continuous infusion of moisture
A change in the direction of the airstream
Lowered vapor pressure in the crystals
Large quantities of wet air come off a nearby mountain
Moisture rises from a lake into the airstream.
Millions of ice crystals form on the surface of a large lake.
Water temperatures drop below freezing
atmospheric temperatures above the freezing point
too much moisture in the air
too much wind off the mountains
ground temperatures below the freezing point