Port Elizabeth of Yore: Effect of the Krakatoa Explosion on the Tides

If Krakatoa was not amongst the top three greatest volcanic explosions of all time, I do not know what could have been. On a pure loss of life comparison basis, Krakatoa only resulted in 36,000 deaths versus 230,000 for the Indian Ocean tsunami on 26th December 2004. Certainly, the effect of Krakatoa was felt was as far afield as Port Elizabeth and South America.

Even though its effect on Port Elizabeth was not very significant, in one person’s life it was very important but not life threatening. 

Main picture: Contemporary map of Krakatoa

The story of Krakatoa
Our story happens at the precise geographic location of 6 degrees 6 minutes south latitude, 105 degrees 25 minutes east longitude, which is in the ocean near the nation of Indonesia. This nation is composed of 18,307 islands, including Sumatra to the west of Krakatau and Java to the east.

The Dutch had colonized the area, and were in control in the 1880s. They strung together the various islands in the area, forming one administrative region—which, with some adjustments, became the nation of Indonesia. However that is not where the history of Krakatoa begins (“Krakatau” as the locals called it; an English newspaper printed it that fateful summer of 1883 as “Krakatoa” and the name stuck). For these purposes, I will use the correct spelling.

Krakatoa after the paroxysm
Above: Krakatau after the paroxysm

From the time of an explosion in 1680, Krakatau occasionally issued small wisps of cloud and smoke for the next 200 years. Early on the morning of Thursday, May 10, 1883, things changed. Just after midnight the lighthouse keeper at First Point, a rocky headland on the southeast side of the Sunda Strait, felt a tremor in the air. The lighthouse seemed to shift on its foundations. The sea whitened, appeared to freeze briefly (like a depth charge going off under the surface), became oddly smooth, shivered slightly and returned to the usual motion of the waves.

Five days later it happened again. This time it was stronger, and was felt to the west as well, in eastern Sumatra and western Java. One Dutch official in the Sumatran town of Ketimbang was awakened by the thudding, rumbling bangs under his feet on May 15, and five days later filed a report.

The ships were the next to notice. The Sunda Strait was then, as now, a very busy waterway. There were at least 10 ships in the vicinity when Krakatoa’s first eruption began in May 1883. Each captain had a story to tell. Several reported large amounts of volcanic ash falling all over their ships. One told of his compass spinning crazily, finally settling at least 12 degrees off course, caused by the extremely high iron content in the ash. Dozens of other reports appeared, some official, some private.

 In the Javanese coastal town of Anjer, fishermen came home that day with tales about the beach splitting wide open, spewing black ash and red-hot stones into the air. Two Dutch officials, disbelieving, raced out to the island in a small boat. They dodged floating pumice and massive charred tree trunks in the ocean, saw horrific thick clouds of volcanic ash and the beach itself on fire.

Map showing the remnant of Rakata Island (now called Krakatau Island) after the 1983 explosion and collapse and the new volcano of Anak Krakatau that subsequently emerged from Krakatau's sunken c
Above: Map showing the remnant of Rakata Island (now called Krakatau Island) after the 1983 explosion and collapse and the new volcano of Anak Krakatau that subsequently emerged from Krakatau’s sunken caldera

Two days later, it all calmed down. After six weeks a Dutch exploration mission landed on Krakatau and examined the still charred island. They climbed the volcano’s crater, burned the soles of their shoes, coughed through the sulphuric foul-smelling air and returned safely. On Aug. 11 a Dutch army captain, ordered to perform a geologic survey on the island, landed and spent two days. He left late on Aug. 12, reporting that all three peaks were emitting smoke and vapour. No less than 14 vent holes, or fumaroles, on the sides of the peaks were smoking. He concluded that Krakatau could erupt again at any moment.

Two weeks later, the island proved him right.

On Sunday, Aug. 26, things were pretty much normal in the town of Anjer. Until 1:06 p.m. The telegraph agent for the port was sitting on the veranda of the Anjer Hotel smoking his cigar, looking out to sea, when he heard an explosion. He immediately looked to his left and saw an enormous cloud of white smoke spewing from the mountain. The sea thrashed in turmoil, the water action unlike any tide known to man. Within minutes the town was enveloped in volcanic dust and ash. The sun was blotted out.

Ships in the area tried desperately to steam out of danger, dodging showers of rock and ash. One Dutch warship was picked up by the huge tidal waves generated and thrown 21⁄2 miles inland on Java. A British ship anchored in Batavia (80 miles east) reported “electrical disturbances” in the huge cloud mushrooming over the mountain, and estimated that the column of smoke this time was more than twice as high as in May—reaching over 17 miles up.

 By 8 p.m. Sunday, the ocean began to cause the most grief. As the explosions continued and intensified, the sea itself was churned up at unfathomable levels. In Ketimbang residents fled in terror, up the mountainsides, away from the rampaging walls of water. Tsunamis over 130 feet high raced from the island at 60 miles per hour. Reaching the Sumatran shore, they slowed to 20 miles per hour and, slicing inland, slowed further still.

Contemporary drawing of Krakatau
Contemporary drawing of Krakatau

One family literally outran the waves up the mountain. They dodged chunks of smoking pumice hurtling from the sky, burning like meteorites. The mud and jungle reached out to slow them; the wife felt her throat constricting, and reached to find the reason for her difficulty. Leeches had attached themselves to her neck like some grotesque jewellery. This family reached its summer hilltop cottage at midnight all safe—husband, wife, three children and household servants. Thousands of others were not so fortunate.

Four more gigantic explosions were still to come. The first was at 5:30 a.m., Monday, Aug. 27. Forty-five minutes later, Ketimbang was destroyed by a monster wave. Shortly afterward Anjer suffered the same fate. The second explosion came at 6:44 a.m., 41 minutes after what should have been dawn that day. At 8:20 a.m., a third, terrible explosion was felt 80 miles away in Batavia. Buildings began to sway and “crackle,” some residents said.

Unimaginably destructive force
Then, at 10:02 a.m., in a culminating, majestic, awful roar that was the loudest noise that has been reported since human beings have inhabited this planet, the majority of the island of Krakatoa simply vanished. Six cubic miles of rock were blasted out of existence.

Captain Sampson of HMS Norham Castle, steaming near Sumatra, wrote these words in his log: “A fearful explosion. A frightful sound. I am writing this in pitch darkness. We are under a continual rain of pumice-stone and dust. So violent are the explosions that the eardrums of over half my crew have been shattered. My last thoughts are with my dear wife. I am convinced that the Day of Judgment has come.”

COLLECTIE_TROPENMUSEUM_Groot_brok_koraal_uit_zee_dat_bij_Anjer_op_land_is_geworpen_na_de_uitbarsting_van_de_Krakatau_in_1883._TMnr_60005541

He and his crew survived. Many did not: 165 villages were destroyed; 36,417 people died—almost all of them drowned in the gigantic tidal waves following the explosion.

The eruption produced two kinds of shock waves. The first was a sudden burst of air pressure measured by a myriad of instruments in that age of immense interest in the new science of meteorology. That air pressure wave circled the earth seven times, finally dying away 15 days later as an echo too faint to measure! It travelled at the speed of sound (which varies with altitude and air pressure)—between 674 and 726 miles per hour.

The ocean waves (tsunamis) comprised the other shock wave. The town of Merak, 30 miles east of Anjer, lost all but two of its 2,700 residents—all drowned.

One woman in Ceylon (now Sri Lanka), 2,000 miles away, was swept off the harbour sandbar when the wave hit the port city of Panama. She was deemed the most distant fatality.

LondonNews_1883_Krakatau

The waves were distinctly measured at what seemed impossible distances. Over 3,000 miles away, in Port Elizabeth, South Africa, the wave was still four feet high when it arrived. A German South Polar expedition on South Georgia Island saw the icebergs lift 15 inches, a dozen times. Near the celebrated French resort of Biarriz, 10,720 nautical miles from Krakatau, seven undulations in the ocean, each 3 inches high, were measured. The wave finally died in the English Channel—at Devonport, England, where the harbour authorities witnessed the last vestiges of Krakatoa’s explosion wave, 11,800 miles distant.

Then there was the sound. The explosions were heard in Saigon, Bangkok, Manila and Perth—each nearly 2,000 miles away. Eighteen witnesses in Ceylon (also 2,000 miles away) reported the explosions. Stockmen driving their cattle across the Hammersley Range in Western Australia reported what they thought was artillery fire to the northwest.

On the island of Rodriguez, 350 miles from Mauritius, in a storm blowing in from the southeast, many of the island’s 5,000 residents distinctly heard the explosions. They, too, thought they were hearing distant artillery fire. Rodriguez is 2,968 miles from Krakatau.

Effect on Port Elizabeth
At the time of the Krakatau explosion, Captain Francis Skead was the Harbour Master at Port Elizabeth. Far away – 4690 miles to be exact – the explosion occurred. On the night of 27th August 1883, the tidewaiter at Port Elizabeth’s harbour was dutifully performing his duties when he recorded a bizarre reading. It distinctly indicated that the harbour had experienced three high tides during the night.

Capt F Skead, Harbour Master 1866-1887
Capt F Skead, Harbour Master 1866-1887

What option did the Harbour Master have but to suspend the deluded tidewaiter on suspicion of being drunk on that night? It was only when he received information of similar surreal readings of an additional tide being reported, did he relent.

Interestingly, a publication entitled Krakatau: The Volcanic Eruption and its Effects includes the tidal records of Port Elizabeth among its statistics. These were the recordings presumably made by the “drunken official”. A year later, pumice stone was reported along the South African coastline, also presumably as a result of Krakatau.

Recordings by tide gauges at Port Blair in the Andaman Islands and at Port Elizabeth, South Africa (Modified after Wharton & Evans, 1888)

Sources
Krakatau and Port Elizabeth by Hans Huisman in Looking Back date March 1989
Krakatau: The Volcanic Eruption and its Effects by Tom Simkins and Richard S. Fiske
http://www.drgeorgepc.com/Tsunami1883Krakatau.html
Krakatoa-Preparing for the Future? by Doug Johnson

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