|Fishing in freshwater|
Fishing and swimming
Fishing is one of the most popular freshwater activities, with over 44 million anglers (people who fish) in the United States. Fish live in almost every lake, river, and stream in the United States, which makes fishing possible for most Americans.
There are two main types of freshwater fishing: fly fishing and spin fishing. The form of fishing used depends on location, the type of fish, and the body of water. Fly fishing is most popular on rivers and streams. Popular types of fish for freshwater fly fishing include trout, bass, and salmon.
When fly fishing, the weight of the fishing line carries the fly, or lure, out into the stream. A series of arm motions whip the fishing line overhead like a bullwhip, simulating the movement of the prey. Fly fishers lure fish with artificial flies and other artificial water-loving insects that are the natural prey of river fish.
In spin fishing, weights called sinkers are attached to the line and carry the hook and artificial lure out into the water. The hook then sinks in the water and the lure spins as the angler reels in the line impersonating an attractive meal to the fish. Trout, salmon, bass, and pike are popular targets for spin fishers.
Swimming is another popular freshwater recreational activity. The principle of buoyancy explains how humans can swim instead of sink in the water. Buoyancy is the ability of an object to float in a liquid. Water exerts an upward force, called buoyant force, on every object that is submerged in it.
An object will float if this buoyant force is greater that the downward force of gravity (attraction between all masses). The object will sink if the weight of the object is greater than the buoyant force.
The ancient Greek mathematician and scientist Archimedes (287 b.c.e.-212 b.c.e.) realized that the density of the object determines whether or not an object will float. Density is an expression of the mass of an object within a given volume.
A piece of steel has a greater density than a piece of Styrofoam of equal size. Archimedes determined that a solid object would float if its density was less than the density of water. Swimming is possible because the human body is less dense than water.
Boating comes in several forms: sailboats; motorboats; and personal watercraft or jet skis. Buoyancy also explains how a ship made of steel can float even though steel is denser than water. The density of the overall shape of an object determines if it will float. A ship is constructed so that most of the interior is filled with air.
This makes the overall density of the vessel less than the density of water. A simple experiment involving a piece of modeling clay and a glass of water demonstrate how this principle works. The clay will sink if it is rolled into a ball and placed in the water, but the clay will float if it is flattened, approximating the shape of a boat.
Sailboats harness the energy of the wind in sails and the energy in the water to propel them through the water. When wind blows along the sails it creates aerodynamic lift, much like on an airplane. Trimming (adjusting) the sails harnesses this lift in a manner that moves the boat in the water.
Without a keel or centerboard (the structure that protrudes from the bottom, or hull, of a sailboat), the wind would blow the boat sideways. The keel primarily acts as a stabilizer. Water passing over the keel also provides lift that counteracts the force of the wind. Together, these forces push the boat forward.
Speedboats have large engines that propel the boat through the water at high speeds. Speedboats are also known as motor-boats or powerboats. These boats are used to zip around on rivers and lakes, pulling water skiers or wakeboarders. Water skiing is where a person holds onto a rope that is attached to the boat while wearing a pair of skis.
The boat then pulls the person along the water. Wakeboarding is similar to water skiing, but it involves a single, larger board rather than two skis. Many fishermen also use motorboats to travel on lakes and rivers in order to reach their favorite fishing spots.
Pontoon boats and houseboats are larger forms of motorized boats. A pontoon boat has two long, hollow tubes running the length of the boat. These tubes are called sponsons and help provide buoyancy and reduce rocking. Pontoon boats have a flat deck and have an open, boxy shape, making them stable in calm waters.
Pontoon boats have motors, but move much slower than speedboats and are used for leisurely cruising and fishing on lakes and rivers. Houseboats are large, enclosed boats with wide hulls to decrease rocking motion and maximize interior space. Many people vacation on houseboats, and some people live on houseboats throughout the year.
Personal watercraft, or jet skis, are small, motorized boats that usually carry one to three people. Riders straddle a personal watercraft as if riding a horse. Personal watercraft are lightweight and can accelerate quickly. As of late 2003 however, personal watercraft were prohibited in 358 of 379 water recreation areas in the U.S. National Park system because of the noise they generate.
Rowing, canoeing, kayaking, and rafting
A canoe is a boat that is pointed at both ends and typically has a completely open top, or deck. People sit or kneel in a canoe and use a paddle with a single blade to move the canoe through the water. A canoe usually holds several people.
A kayak is a boat that is pointed at both ends and has a closed deck except for a small hole where the paddler sits. A kayak paddle has two blades, with one on each end. A kayak usually holds only one person, but some models can carry two people. In order to steer the kayak, it is necessary to use the entire body for balancing and leaning along with the paddle.
A raft is a flat-bottomed boat, which is usually inflated with air. Several riders use paddles with single blades to move and steer rafts. Rafts are flexible, so they are often used in water that may contains rocks. If the raft hits a rock or goes over a small waterfall, the raft will bend instead of breaking.
Kayaks and rafts are often used for riding down river rapids, which are stretches of fast moving water on a river or stream. Rapids form from erosion (wearing away by wind or water), when water erodes rocks in a river at different rates. The soft rocks erode first, creating a steeper gradient (the angle of slope down which a river flows) for the river to flow down among the remaining harder rocks.
Whitewater rapids are formed as the water increases speed in order to move along the steeper pathway among the harder rocks. When people travel down rapids, these sports are referred to as whitewater kayaking and whitewater rafting. Specially made canoes may also be used for whitewater canoeing.
Thermal springs and spas
Thermal springs (natural flow of groundwater), also commonly called hot springs, were considered healing waters by many ancient cultures and still are by many modern cultures. Thermal springs produce water that has been heated by the earth to a temperature of 70°F (21°C) or above.
The ancient Romans constructed elaborate bathhouses, or spas, at the sites of thermal springs, and hot springs continue to be a major attraction in modern times. Modern spas often locate at the source of thermal springs, making hot springs popular destinations.
The water that flows from thermal springs becomes heated by geothermal warming in one of two ways. Geothermal means relating to heat generated from the center of the earth. The presence of underground volcanoes near the surface of the Earth can heat the water. Iceland is famous for its numerous volcanic thermal springs.
Thermal springs can also be produced by rainwater seeping deep into the earth and then rising quickly. One example of this method is found in Hot Springs, Arkansas, where rainwater has seeped into the earth for thousands of years.
The water seeps down to a depth of 6,000 to 8,000 feet (1,829 to 2,438 meters) below the surface and warmed by the earth’s internal temperature. Cracks in rocks then allow the warmed water to return to the surface in less than a year. Because the water’s return trip is quick, the water loses little heat and surfaces at about 147°F (63.8°C).
Tourism at Niagara Falls
Niagara Falls actually consists of two main waterfalls. The larger waterfall is Horseshoe Falls, or Canadian Falls. Horseshoe Falls, shaped like a horseshoe, is 167 feet (51 meters) high and 2,600 feet (792 meters) across.
Over 600,000 gallons of water flow over Horseshoe Falls every second. On the opposite side of the falls, American Falls is 176 feet (54 meters) high and 1,060 feet (322 meter) across. Over 150,000 gallons flow over American Falls every second.
The waterfalls at Niagara were formed nearing the end of the last Ice Age about 12,000 years ago, when melting ice flowed into what is now the Niagara River. The river flowed over the Niagara escarpment (cliff), slowly wearing away the underlying rocks until the falls was carved upstream to its current position.
Many parts of the country enjoy recreational activities on frozen lakes and ponds. Ice skating and ice hockey are activities that can be enjoyed on frozen bodies of freshwater. Ice fishing is also another popular activity in some parts of the United States.
Ice fishing involves cutting a hole in the ice on a lake or river and dropping a fishing line into the water below the ice. Liquid water is denser (heavier per unit) than ice. This explains why ice floats and forms on top of the lake in winter.