Krakatau: Ordeal by Fire and Water

Krakatau: Ordeal by Fire and Water!

Until nearly the end of the nineteenth century volcanology had scarcely achieved the status of a science. But then came the awesome explosion of Krakatau (formerly Krakatoa), which made its mark, one way or another, on every one of the earth's 197 million square miles.

One of a group of volcanic islands, Krakatau lay in the Sunda Strait between Java and Sumatra, a collision zone between two of the great plates that make up the earth's crust. Krakatau had already undergone several eruptions, the greatest occurring about 500,000 years ago, with only Stone Age Homo erectus (Java ape man or pithecanthropus) as witness. On this occasion the island's original 6,000—foot—high cone vanished into dust, leaving several small island fragments around the rim of the caldera, a craterlike basin created by the collapse of the volcano. Ash and lava continued to bubble up from the caldera's southern rim, until a new half—mile—high cone, Rakata, was created. Eventually two smaller cones, Perboewatan and Danan, developed to the north and united with Rakata. They formed Krakatau Island, five miles long and on to three miles wide.

For centuries the volcano remained quiet. Then in 1680 the smallest of Krakatau's cones, Perboewatan, came to life. This eruption killed off the island's vegetation, and there were two more centuries of silence. The jungle grew back on Krakatau, and as far as anyone knew the volcano was extinct.

Opening Cannonade

On May 20, 1883, Dr. Van der Stok, director of the observatory in Batavia, Java (now Djakarta, Indonesia), was disturbed by rattling and banging of doors, windows, and china at his home. From the north—west came a low rumbling that sounded like distant artillery fire. He correctly surmised that somewhere a volcano must be erupting. He entered this fact in his official diary, as well as the time of day — 10:55 A.M. The rumbling continued throughout the day, and he timed each explosion. He was not alarmed because volcanic eruptions were a part of life in this area of the world. On Java there were forty—nine active volcanoes.

At Anjar, the chief port on the Java shore, the disturbance was much greater, and one of the Dutch officials turned his telescope on the strait to locate the source. He checked the island group of Krakatau and noted that the sky was clear and no cloud rose above the three tiny volcanoes. Krakatau was a calm and peaceful mass of greenery, clothed from base to summit in luxurious forest and tropical vegetation, a landmark for ships coming from the west. The great eruption on this island 200 years before, when the sea had been choked with pumice and the shore resembled a moonscape, was chronicled in local legends.

In the afternoon seamen on the many ships that sailed through the strait's fast shipping lane witnessed more menacing activity. The Dutch mail ship Zeeland passed within five miles of Krakatau, and its crew observed steam and debris spewing from the northern cone. Over the island hung a dark, heavy cloud, out of which came a series of flashes accompanied by unbroken crackling like nonstop machine—gun fire. Sailors on other ships watched columns of ash and steam rising from the volcano and fiery red clusters gushing from its base. Loud detonations made nearby ships tremble, and crewmen within five miles of the island could feel heat radiating on their faces and hands. Although the ships' crews were anxious to move on, the sky became so dark that they were forced to proceed at half speed. Thirty miles from the island a sailor lowered a bucket into the sea and brought up pumice with scarcely a drop of water.

Most people in the area considered Krakatau a burned—out crater slumbering in its old age and were more curious than alarmed as volcanic activity continued unabated throughout the week. The excursion steamer Loudon brought a party of sightseers to Krakatau, where they picnicked and climbed the slopes of the most active cone. They sank up to their calves in ash, sulfur troughs of bubbling mud swirled near their ankles, and a crackling, grumbling column of steam rose in the air above. They climbed to the top and peered into the crater at a vent thirty yards wide from which gushed lava and steam. The more foolhardy adventurers climbed partway down into the crater to gather souvenirs of pumice and lava. As darkness fell, the Loudon steamed away, surrounded by an awe—inspiring spectacle of beauty and grandeur.

A three—week calm was followed by rekindled volcanic activity throughout July, and on August 10 a Dutch official who landed on Krakatau found it too dangerous to carry out a detailed survey. The island was completely devastated; only a few tree trunks remained, and the ground was covered by a layer of ash and sulfur at least two feet deep. All three of the peaks on Krakatau were now erupting.

The fissures underlying Krakatau provided subterranean corridors from deep beneath the earth's crust; during earthquakes a few years before, many new vents had been opened. These conduits were easy escape routes for the huge mass of gas—charred, explosive magma building up in the white—hot chasm below. They were also ports of entry for sea water to seep downward. On contact with molten rock the water entering the magma chamber was transformed into steam and its volume increased enormously. The new vents provided channels for the release of pressure building up below. Liberated gases rose in the volcano's chimney, where magma frothed and bubbled. The rising magma clogged the vents and plugged the chimney.

Above ground, along the shores of the strait, 36,417 people worked and slept, ate and drank, played and quarreled, unaware that they would shortly become victims of nature's greatest catastrophe. Krakatau's three months of menacing prelude were over, and nature's three—ring circus was about to begin.

The Great Explosion

The morning of Sunday, August 26, 1883, broke fine and clear in the Sunda Strait. The sun rose high in the cloudless sky, and faint wisps of steam rose from Krakatau's three small cones. As long as the plugged chimney resisted the impulsive forces from below, nothing of the volcano's fury was evident on the surface. The churning gases at the top of the magma column surged upward with increasing strength and pounded on the plugs like a raging demon that had been held captive for centuries. At 1:00 P.M. the plugs' resistance to the pressure gave out, and the volcano erupted. An explosive pillar of steam and a cloud of debris shot into the air, accompanied by an ear—shattering fusillade.

Within an hour the cloud had risen to seventeen miles, three times the height of Mount Everest. Steam and debris climbed in a thick column, mushrooming out in the shape of a gigantic Christmas tree with the waters of the strait with ominous sound effect. The natives who flocked together on shore were convinced that the end of the world had come. By 3:00 P.M. it had grown dark and the roaring of the volcano had become so relentless that the ground trembled underfoot. Terrifying detonations came every two or three minutes, and the air was charged with sulfurous fumes.

Captain Logan of the ship Berbice recorded in his log at sea:

Midnight — The ash shower is becoming heavier and is intermixed with fragments of pumice stone. The lightning and thunder became worse and worse. Lightning flashes shot past around the ship. Fireballs continually fell on deck and burst into sparks

From the book: 
Our Fascinating Earth