Ever since humans first took to the seas thousands of years ago, sailors have faced numerous dangers. Ancient civilizations tried to explain these dangerous conditions by claiming that they were the work of angry gods or monsters. While scientific explanations have been advanced for dangerous phenomena such as high waves, hurricanes, and treacherous ocean currents (steady flows of water in a prevailing direction), many lives are still lost in the water each year, mainly due to drowning or hypothermia. Hypothermia is a condition where the core body temperature becomes too cold to function properly. Prolonged exposure to waters that may initially seem warm, between 70°–80°F (21°–27° C), can cause death from hypothermia.
Some of the earliest written works make references to the dangers of the seas. In the Odyssey, Greek poet Homer mentions a great whirlpool that a group of Greek warriors encountered on their return home from the Trojan War. Many scholars assume that Charybdis, the whirlpool mentioned by Homer, is a whirlpool that still swirls today between mainland Italy and the island of Sicily. Viking poems refer to another famous whirlpool, the Maelstrom, which lies off the rocky coast of Norway.
Several factors, working alone or together, can create whirlpools. Ocean currents that converge (come together) can cause a whirlpool. Tides and rock formations can create a whirlpool by forcing ocean currents to flow in a circular motion, as in the Maelstrom. Also, constant winds on the ocean can create or contribute to a whirlpool, as in the narrow waters between Italy and Sicily.
Although movies and literature sometimes refer to people or ships being drawn down into a whirlpool, this rarely happens. Whirlpools can pose a moderate danger to small crafts, as they can experience turbulence or even capsize (turn over) in whirlpools. Modern navigation allows ships to avoid large ocean whirlpools. Today, the greatest danger posed by whirlpools is on rivers, where curious boaters often wander too close to whirlpools and quickly find themselves in their midst.
Cape Horn and the Straits of Magellan
Cape Horn and the Straits of Magellan lie at the southern tip of South America where the Atlantic and Pacific Oceans meet. The Straits of Magellan are a narrow passage between mainland South America and Tierra del Fuego, a large island to the south of the mainland. Portuguese explorer Ferdinand Magellan (1480–1521) discovered the Straits of Magellan in 1520 during his trip around the world. The Straits of Magellan are narrow and often experience rough seas due to high winds. The Atlantic and Pacific Oceans are at different levels, which cause churning currents when their waters meet in the Straits of Magellan. These powerful currents caused numerous ships to sink in the Straits of Magellan.
Isaac Le Maire (1558–1624), a Dutch merchant and explorer, discovered Cape Horn in 1615. Le Maire was looking for a different and safer route between the Atlantic and Pacific Oceans. Le Maire found a different route in what is today called Cape Horn, but it did not prove to be much safer than the Straits of Magellan. Cape Horn has violent weather patterns as a result of the meeting of the Atlantic and Pacific Oceans. Cold air moving north from Antarctica also contributes to the foul weather. Large waves, some over 65 feet (20 meters) tall, often sank ships that tried to round Cape Horn's rough seas. The opening of the Panama Canal in 1914 eliminated the need for most ships to travel through the Straits of Magellan or around Cape Horn in order to pass between the Atlantic and Pacific oceans.
Hurricanes, typhoons, and cyclones
A hurricane is any organized storm with sustained winds of 74 miles per hour (119 kilometers per hour) or greater in the Atlantic Ocean, Gulf of Mexico, Caribbean Sea, or eastern Pacific Ocean. Winds gusts in the strongest hurricanes approach 200 miles per hour (322 kilometers per hour). Hurricanes include circular bands of clouds that slowly swirl around a central core of low atmospheric pressure (the pressure exerted upon Earth's surface by its atmosphere at a given point), called the eye. A hurricane may be hundreds of miles (kilometers) across, but the eye of the storm is typically only 10–30 miles (16–48 kilometers). Winds are strongest around the eye and weaken further out from the eye. A hurricane that occurs in the Indian Ocean is called a cyclone, and those in the middle and western Pacific are called typhoons.
Hypothermia is a condition where the body becomes too cold to function properly. The human body strives to maintain a constant internal temperature at or near 98.6°F (37° Celsius). Unlike some animals that live in the cold arctic climates, humans do not have a layer of fat called blubber that surrounds the body. Humans must rely on layers of clothing to keep their bodies warm. If clothing is insufficient or becomes wet, a condition called hypothermia may occur.
Many people have experienced mild hypothermia, perhaps while playing in snow. Moderate hypothermia occurs when body temperature is between 97–95°F (36.1–35°C). Symptoms of mild hypothermia include shivering, numbness in the hands, and an inability to perform complicated tasks with the hands. A person experiencing these symptoms should go indoors or try to warm herself immediately. More severe problems may occur if body temperature continues to drop.
Severe hypothermia occurs when the body temperature drops below 90°F (32.2°C). Hypothermia causes the body to lose proper mental and physical functions. If hypothermia continues for a long period or under extremely cold temperatures then death may result. Every year about 700 Americans die from hypothermia.
One reason that hypothermia claims so many lives is because many people have the mistaken belief that hypothermia only occurs by falling into cold water. Hypothermia can occur from merely being outside in the cold without proper clothing. Hypothermia can also occur at any time of year, even during the summer. Water temperatures between 70–80°F (21.1–26.6°C) can lead to hypothermia, and even death, within a matter of hours. In water less than 32°F (0°C), death from hypothermia can occur within 15 minutes.
The low pressure of the eye pushes a wall of water in front of the storm called a storm surge. The storm surge is often the most destructive part of a hurricane. Storm surges can sink ships at sea, destroy buildings on the coast, and cause flooding inland.
Hurricanes are divided into categories based on the speed their sustained winds. A category 1 hurricane produces sustained winds of 74–95 miles per hour (119–153 kilometers pr hour) and storm surges 4–5 feet (1.2–1.5 meters) above normal tide levels, enough to flood low-lying coastal roads and buildings. Category 2 storms contain winds 96–110 miles per hour (154–177 km per hour) and produce storm surges 6–8 feet (1.8–2.4 meters) above normal tide levels, enough to flood coastal escape routes (roads and bridges leading away from the coastline) and require some people to evacuate their beachside homes. A category 3 hurricane has sustained winds of 111–130 miles per hour (179–209 km per hour) and storm surges 9–12 feet (2.7–3.6 meters) above tide levels. Storm surges this high can cause major erosion (wearing away) of beaches and destruction of houses and businesses on and near the beach. A category 4 storm produces winds of 131–155 miles per hour (211–249 km per hour) and storm surges 13–17 feet (4–5.1 meters) above normal tide levels. Wave action from category 4 storms can destroy buildings constructed on land less than 2 feet above sea level, and can cause flooding up to 6 miles (10 kilometers) inland. A category 5 hurricane has sustained winds over 155 miles per hour (249 kilometers per hour) and brings a storm surge 18 feet (5.5 meters) or more above normal tidal levels. Besides massive building damage from wave action and winds, damaging floods occur more than 10 miles (16 kilometers) inland, and large-scale evacuations of coastal communities are necessary. Only three Category 5 hurricanes have ever hit the United States as of 2004.
A storm with sustained winds between 39–74 miles per hour (63–119 kilometers per hour) is called a tropical storm. Tropical storms are known for their ability to produce large amounts of rainfall over a short time. An organized storm with sustained winds below 39 miles per hour (63 km per hour) is called a tropical depression. A tropical depression can become a tropical storm and possibly a hurricane.
Nor'easters, or Northeast winter storms, are large winter storms that dump snow and ice on the coastlines of America's mid-Atlantic and New England states. Nor'easters have struck as far south as Florida. Nor'easters typically occur between October and April. Unlike hurricanes, which rotate, a Nor'easter is a single storm line. A single Nor'easter may stretch for over 900 miles (1,448 kilometers). Nor'easters may pack strong winds and waves, causing beach erosion and blizzard conditions in coastal cities. Ships at sea during a Nor'easter often face waves and swells over 50 feet (15 meters) high.
Nor'easters form when warm air from the southeastern United States creates an area of low pressure just off the coast. Northeastern winds pull the warm air in the low-pressure system up the East Coast. The system picks up moisture from the Atlantic Ocean as it moves north. Cold air from Canada then mixes with this moisture-filled air. The product is a line of strong storms carrying snow and ice.
Icebergs are large chunks of ice that break off from glaciers or icepacks (a large expanse of floating ice) and float in the oceans. A glacier is a slow-moving solid pack of ice and snow that forms over thousands of years. Most of the world's glaciers were formed between 10,000 and 15,000 years ago during the last Ice Age. Most glaciers slowly flow toward the sea. When a large piece of a glacier pushes out into the sea, it breaks away from the glacier and becomes an iceberg.
Most icebergs break away from glaciers in Greenland or Antarctica. While the majority of icebergs remain far to the north, out of the way of most ships, every year several hundred icebergs drift into areas containing shipping routes. These icebergs pose a major risk to ships. An iceberg can create a large hole in a ship and cause major damage or even sink the ship. The most famous example of this is the Titanic, which hit an iceberg in the north Atlantic Ocean in 1912. The ship sank within hours, killing more than 1,500 people. Following the sinking of Titanic, several nations formed the International Ice Patrol to search for icebergs and record their positions. Modern technology is also capable of detecting icebergs in shipping lanes during the day and night, and in bad weather as well as clear skies. An instrument called synthetic aperture radar that orbits Earth aboard a satellite (vehicle that orbits Earth) collects and sends pulsed signals back to Earth, where a digital map of icebergs, their size and shape, and their precise location is formed.
Lost at Sea
For thousands of years one major problem plagued sailors: How to tell exactly where their ship was located in the vast ocean. On the open sea there is water as far as the eye can see in every direction. This posed the problem of how to navigate successfully. Navigation refers to the ability to determine the proper position of a ship and the proper direction to sail in order to reach the desired destination. Sailors in ancient cultures solved this problem by never losing sight of land. They would sail along the coast or hop from one island to the next.
This method proved to be impractical as ships became larger and need to move cargo over great distances. Mariners (sailors) soon began to use the stars to guide their ships. However only one's position north or south of the equator (imaginary line around Earth between the North and South Poles) could be determined by using stars. Many ships continued to get lost at sea because they could not determine their east-west position.
In 1592 a Portuguese ship laden with riches was lost on the return trip from India. Six English ships sighted the Portuguese ship and defeated her in battle. The value of the cargo on the ship was roughly half of the amount that the entire English treasury department possessed at the time. In 1707 four British ships ran aground on their return to England. The ships got lost in the fog. Assuming that they were still far from home, the ships continued on through the fog. They soon realized their mistaken when they ran aground near the English coast. Nearly two thousand men died in the ensuing shipwrecks.
In 1714 England's Parliament offered £20,000, or several million dollars in today's currency, to anyone who could figure out a way to calculate one's position east-west of the equator. English clockmaker John Harrison (1693–1776) put forth the unlikely solution: a clock. Harrison's clocks could keep accurate time at sea, allowing sailors to calculate its east-west position through mathematics based on the time in London. Harrison never received the full prize money, but fewer ships got lost at sea thanks to his discovery.
Reefs and rocks
Like icebergs, reefs and rocks near the shore can damage the hull of ships, causing them to spill their cargo and even sink within a short time. A reef is an underwater ridge of rock or coral (tiny marine creatures with hard exterior skeletons) that lies just below the surface. Rocks can be difficult to spot with the eye, and it is nearly impossible to see a reef before a collision. Many modern ships rely on sonar (images produced by sound waves) or satellite technology (images produced by light waves) to detect rocks and reefs, but accidents still occur. In 1989 oil tanker Exxon Valdez ran aground on a reef in Prince William Sound, Alaska, causing an oil spill of 11 million gallons (46.5 million liters) into the Alaskan ecosystem. While the Exxon Valdez was not one of the largest oil spills in history, it did have a major impact on the environment and shipping regulations. The ensuing cleanup cost over $2 billion, and the Prince William Sound ecosystem continues to recover to its former level of biodiversity (range of varying plant and animal species).
Animals in the seas
Although sharks, jellyfish, and other sea animals do injure people in the ocean every year, the number of these attacks are usually sensationalized. Between 70 and 100 shark attacks on humans occur throughout all the oceans worldwide each year. On average, five to ten people die every year as a result of these attacks. Americans are over 300 times more likely to be killed by a car crash involving a deer than by a shark attack in the ocean. Many coastal states monitor shark populations in beach areas where sharks and humans mix by regularly counting and mapping shark populations according to geographic features in their habitat. Areas can use this data to issue shark advisories to beachgoers when shark populations are observed to be greater than the normal number of sharks.
Mines are explosive devices that usually explode when an object makes contact with them. While many people are aware of the danger posed by land mines, sea mines can be equally destructive. Sea mines typically float just at or below the surface of the sea. This makes sea mines almost invisible to an approaching ship. Once the ship runs into the mine, the mine explodes.
During wartime sea mines serve a defensive purpose. They prevent enemy ships from approaching too close to shore. Mines remain a hazard in peacetime because the position of mines may be forgotten or the mines may drift way. Often a defeated nation is left with little resources to pick up sea mines laid by its military. Sea mines can also remain active for many years. In 1988 a U.S. navy ship, Samuel B. Roberts, ran into a sea mine in the Persian Gulf in the Middle East. The mine had been planted about 70 years earlier during World War I (1914–18). The mine caused $96 million in damage to the ship.
In order to avoid setting off mines many naval vessels scout ahead for them. This process slows down ships traveling through areas thought to contain mines. When detecting sea mines, ships use sonar or a helicopter with sonar flies in front of the ship. Divers investigate any suspicious objects found. If the object is a mine then specially trained divers disable it. The U.S. Navy is currently developing robots that can find and disable mines.
Most jellyfish stings cause pain, but they rarely kill humans. One exception is the sea wasp or box jellyfish (Chironex fleckeri) that lives in the waters off northern Australia and Southeast Asia. This species of box jellyfish carries venom (poison) in its tentacles powerful enough that a single sting can cause death without prompt medical treatment. All jellyfish species however, are passive hunters; they do not attack prey for food, but wait until a potential food source (including humans) bump into their tentacles.
Joseph P. Hyder
For More Information
Gemmell, Kathy, et al. Storms and Hurricanes. Tulsa, OK: E.D.C. Publishing, 1996).
Lundy, Derek. Godforsaken Sea: The True Story of a Race Through the World's Most Dangerous Waters. New York: Doubleday, 2000.
Morris, Neil. Hurricanes & Tornadoes: Wonders of Our World. New York: Crabtree, 1998.
Bruneau, Stephen E. "Icebergs of Newfoundland and Labrador: Frequently Asked Questions with Short Answers and Pointers." Newfoundland and Labrador Tourism.http://www.wordplay.com/tourism/icebergs/ (accessed on August 27 2004).
"Hazards: Hurricanes." Federal Emergency Management Agency.http://www.fema.gov/hazards/hurricanes/ (accessed on August 27, 2004).
"Hurricanes." FEMA for Kids.http://www.fema.gov/kids/hurr.htm (accessed on August 27, 2004).
"International Ice Patrol (IIP): Frequently Asked Questions." United States Coast Guard: International Ice Patrol.http://www.uscg.mil/lantarea/iip/FAQ/FAQ_Category.shtml (accessed on August 27, 2004).
"International Shark Attack File." Florida Museum of Natural History.http://www.flmnh.ufl.edu/fish/Sharks/ISAF/ISAF.htm (accessed on August 27, 2004).
"National Weather Service, Tropical Prediction Center." National Hurricane Center.http://www.nhc.noaa.gov (accessed on August 27, 2004).
"Oil Spill Facts." Exxon Valdez Oil Spill Trustee Council.http://www.evostc.state.ak.us/facts (accessed on August 27, 2004).
Venanzangeli, Paolo. "Cape Horn the Terrible." NauticalWeb.http://www.nautica.it/charter/capehorn.htm (accessed on August 27, 2004).
Winchester, Simon. "In the Eye of the Whirlpool." Smithsonian Journeys.http://www.smithsonianmag.si.edu/journeys/01/aug01/feature_full_page_1.html (accessed on August 27, 2004).