In many northern
states the winters are so cold that the lakes freeze right over. In
Minnesota, Michigan, and Maine, the ice in these lakes can freeze two to
three feet deep. When the ice is that thick it becomes possible to
actually drive a car or truck across the ice. While driving on ice
sounds like something that people would do just for fun, a lot of people
drive across frozen lakes for very practical reasons. For example, there
are people who live year-round on islands within these northern lakes.
In the middle of winter the only practical way of traveling to the
mainland is by driving across the frozen lakes. Actually, when the lake
is frozen two to three feet deep, this is a perfect opportunity for
people living on islands to transport large objects onto or off the
islands. Say, for instance, you owned a cabin on a small island in the
middle of a lake in Michigan. Suppose you decided that you wanted to
build an extra room onto the cabin.
Transporting all the building materials onto the
island using a boat would take a lot of work and expense. But if you
waited until winter, you could easily drive all the building materials
across the lake. How can you tell if a lake is frozen solid enough to
drive on? The surest way to know is to wait until several other cars and
trucks have safely driven across the ice. Even then, you should always
be extra careful when driving across a frozen lake. It's possible that
one section of the lake has currents that prevent the lake from freezing
solid. Or there might be a river or stream that brings slightly warmer
water into one part of the lake. So even though most of the lake was
frozen solid, one section of the lake could have thin ice.Usually it
takes at least two to three weeks of very cold weather before deep ice
is formed on a lake. Here in the northern United States, deep ice
doesn't form until mid-January, at the earliest. (In northern Canada and
Alaska lakes sometimes freeze solid as early as November or December.)Do
the tires of cars slip when they drive across ice? Yes, sometimes they
do. But almost every car and truck that drives on ice has snow tires,
which creates extra friction between the tires and the ice. Some people
also choose to put chains on their tires, which gives the tires an even
stronger grip against the ice. After a few cars have driven across a
particular path on a lake the ice actually becomes a sort of road. If
you walked up to such a road and did not know that the road was
traveling over a lake, you might never suspect that the cars and trucks
are actually driving across solid ice.
|