On November 4, 1799, the British battleship "Skypetel" and the Danish battleship "Yaomingburg" and eight merchant ships were at the southern tip of Africa at the Cape of Good Hope. The Cape of Good Hope was shipwrecked, killing more than 400 people on the Petel Sky alone. In this disaster, both warships and civilian ships suffered misfortune, which is rare in the history of shipping.
The climate of the Cape of Good Hope is changeable, and shipwrecks are frequent. Known as the "Crew's Grave", it has become the most dangerous road in the world.
Dias (1450 – May 29, 1500), who led a fleet to the southernmost tip of the African continent, discovered the Cape of Good Hope
The "Cape of Good Hope" is not easy to get along with
The discovery of the Cape of Good Hope is closely related to the Age of Discovery. In August 1487, the Portuguese navigator Dias led two light galleons and general transports, and at the behest of King João II of Portugal, discovered the "Cape of Good Hope" in January of the following year, while exploring a new route from Europe to India. Good wishes).
In fact, the Cape of Good Hope is not easy to get along with. In 1716, a storm at the Cape of Good Hope destroyed 42 Dutch ships, causing a fortune of 40 billion francs to sink to the bottom of the sea. Donald Dias, the discoverer of the Cape of Good Hope, is even buried here. Even in modern times, the Cape of Good Hope remains desolate. According to incomplete statistics, since the 70s of the 20th century, as many as 11 10,000-ton giant ships have sunk at the Cape of Good Hope. Behind the beauty of the Cape of Good Hope hides the crew's constant nightmares.
Above the Suez Canal
Dangerous "killer wave"
Due to the tonnage limitations of the Suez Canal, naval ships exceeding 250,000 tons must detour the Cape of Good Hope. Giant ships hovering are sometimes hit by large waves, causing shipwrecks and deaths, resulting in heavy casualties. Even the world-class oil tanker "World Honor" was suddenly hit by a huge wave more than 20 meters high in the sea area of the Cape of Good Hope, broke in two, and unfortunately died.
The well-informed crew dubbed this elusive wave the "killer wave." It is characterized by the sudden appearance of a large wave or group of large waves with a height of 15-20 meters on the calm sea, which is difficult to defend against. The leading edge of the killer wave is steep and the trailing edge is gentle, like a wall of water. If the boat and the wave move in the opposite direction, a similar result to "world honor" suffers. If the boat and the wave remain parallel, the huge wave may capsize the boat.
According to expert estimates, the pressure when the 12-meter-high wave breaks is 6 tons per square meter. The structural pressure resistance of modern ships is usually designed to be 15 tons, while the killer wave water wall pressure reaches 100 tons per square meter. The difference between the two is several times, which is also one of the factors that produce the powerful power of the "killing wave".
Above_ Waves at the Cape of Good Hope
The exact cause of the "killer wave" is not yet known. As for the wave itself, at some point there will be a sharp concentration of energy. The center wave absorbs the energy of neighboring waves, causing it to expand rapidly. In addition, the initial wave can have a constant wavelength and frequency. The wavelength and propagation speed can vary due to wind or resistance. Long-wave speeds are faster. After catching up with the short wave, the two peaks connect to each other and merge into a large wave.
Killer waves are also associated with ocean currents. Professor J.K.'s research on Mallory of the University of Cape Town in South Africa found that the huge waves that caused the shipwreck always came from the southwest, and the shipwreck sailed southwest, so the ship was hit head-on by the huge wave. In addition, the Agulhas Current, originating in the Indian Ocean, flows along the southeast coast of South Africa. This stream has a flow rate of 80 million tons per second and a flow rate of 1 to 2 meters per second. It is one of the fastest currents in the world. The direction of the current coincides with the direction of the ship and opposite to the direction of the huge wave. The overlapping effects of ocean currents and large waves can cause catastrophic damage to ships. Complex, ferocious waves pose a serious threat to ships crossing the Cape of Good Hope.
Above_Distribution of world ocean currents
Haunted Saijo
The local weather makes the sea conditions at the Cape of Good Hope very dangerous. The Earth's rotation controls the flow of air. The Cape of Good Hope is located in the mid-latitudes of the Southern Hemisphere, and air currents should be transported to the poles. As the Earth rotates from west to east, this northerly wind creates a deflection force that acts on the right side of the forward direction. The north wind turns to the northwest wind, and the higher the latitude, the greater the deflection force, forming a westerly wind belt. In addition, the temperature difference between day and night in the mid-latitudes is large, the heat consumption is large, and the upper and lower convection is strong, which further fuels the wind.
It is also not recommended to underestimate the low pressure, except in the western belt, which moves south from the Atlantic. The air pressure in these low-pressure centers reached 964 hPa, equivalent to the level of an early typhoon in the Northern Hemisphere. Low pressure is blocked by high pressure or stronger low pressure. The speed is fast and slow, and the behavior is erratic. In some areas, there are basically 3 to 7 air pressure troughs hovering, forming low-pressure clusters. They often merge or overlap to create stronger low pressures. Individual depressions can cover areas from Antarctica to the southern coast of South Africa.
The combination of wind and waves has undoubtedly worsened the sea conditions in the area where the Cape of Good Hope is located. Unwilling to be lonely, the Egulas Current joined the battle of wind and waves. Waves deform and break into deadly waves under the action of winds, waves and ocean currents. The Cape of Good Hope is dominated by westerly winds, which not only increases the unpredictability of sea conditions, but also creates unresolved deadly waves.
Map above_Cape of Good Hope
Insufficient scientific research
The lack of research on waves has led to a relaxed guard against the dangers of waves. For nearly a century, meteorologists, oceanographers, and ship designers have used standard linear model mathematical systems based on Gaussian functions to calculate and predict wave heights. The model shows that there is a direct relationship between wind intensity and wave height, and the maximum wave height changes regularly according to the average wave height. Huge waves 30 meters high only appear once every 10,000 years. Storm surges up to 20 meters high are so rare that they are not included in the official sea state map. With the development of science and technology, advanced meteorological observation and forecasting systems have been put into use, and sailing ships can predict the weather in advance and avoid storms. The high-strength modern hull is also enough to cope with rough waves above 14 meters.
The truth soon came out. In 1826, a French naval captain and scientist observed a 33-meter-long wave. Three colleagues witnessed this terrible wave. At that time, it was widely believed that waves could not exceed 9 meters, and famous scientists scoffed at this. In 1995, a suction caisson offshore oil rig was commissioned in Norway. A large number of advanced sensors are installed on the platform to monitor its stability. At 3:20 p.m. on January 1 of that year, all sensors recorded a huge wave hitting the platform head-on, with a speed of 72.4 kilometers per hour and a wave height of 25.9 meters.
Above_Cape of Good Hope landscape picture
Since then, people have begun to study waves using the scientific method. In 2001, the European Space Agency used two satellites to monitor the world's seas for three weeks and detected 10 waves over 25 metres, some as high as 30 metres. Research from the Australian National University shows that there are at least 10 such waves in the world at any given time. Other scientists have found that about 3 out of every 10,000 waves reach a height of 25 meters. This wave of non-compliance includes the killer wave at the Cape of Good Hope.
Although the understanding of waves has come a long way, the reality remains grim. It is technically difficult to improve the structural strength of ships in the short term. In order to cope with the extremely low probability of super waves, it is obviously uneconomical to invest heavily in the modification of ocean liners. However, the wave research boom triggered by killer waves makes people face up to the gap between reality and theory, which creates a good atmosphere for further research.
Today, a map of southern Africa states: "Unusually large waves, up to 20 meters high and deep waves, often occur at the edge of the continental shelf and in the sea within 20 miles of the coast." "When the westerly wind is strong, the sea conditions are harsh. Air pressure is low, so such large waves are more common. "This is not only a reminder of safe rowing, but also a wake-up call for human self-expansion."
Author: Ji Baidanghei Proofreader/Editor: Lilith
Reference:
[1] Wu Keqin, "The Cause of the Great Waves at the Cape of Good Hope"
[2] Cai Haiyan, "Murderous Wave"
[3] Dong Shouli "A Brief Discussion on the Meteorological and Sea Conditions of the Cape of Good Hope and Its Adjacent Seas"
[4] Institute of Physics, Chinese Academy of Sciences "Rogue waves, monster waves, water walls, killer waves, once only existed in myths and legends of marine demons"
The text was created by the History University team, and the illustrations came from the Internet. The copyright belongs to the original author.