The Unmaking of an Island

The dramatic eruption of Krakatoa (or Krakatau in Indonesian) in 1883 was, as our sister blog Headlines and Heroes describes it, “one of the first global catastrophes.” By its very destruction, this small Indonesian island was thrust onto the world stage, its name becoming almost shorthand for volcanic disaster.

Geologist Rogier Verbeek, who had briefly surveyed the islands for the Governor-general of the Dutch East Indies three years before the eruption, visited again in 1884 and published a report on his observations. Along with Verbeek came a team of experts including topographer J. G. de Groot. De Groot produced several maps which were published in conjunction with the report, and which eventually made their way into the collections of the Geography and Map Division.

The island of Krakatau lies in the Sunda Strait, a narrow passage of water between the Indonesian islands of Sumatra and Java. Though sometimes overshadowed by the nearby Strait of Malacca, the Sunda Strait served for centuries as an important artery in the spice trade. Like many areas around the rim of the Pacific Ocean, the Indonesian archipelago is prone to both seismic activity – earthquakes – and volcanic eruptions. The Krakatau volcano had likely erupted at least ten times in recorded history prior to 1883.

The first map from Verbeek’s report is perhaps the most dramatic. Figure 1 shows Krakatau and neighboring islands Verlaten (today called Sertung) and Lang (today Krakatau Kecil). The islands are drawn as they appeared in October 1883 – three islands of roughly similar size spaced around an open area of water, dotted by a few rocks. Ghostly pink outlines also appear on the map, of the islands’ earlier states. While Verlaten and Lang have both grown in size, Krakatau is dwarfed by the fading image of its past self; most of the island has been utterly obliterated.

Figures 2 and 4 show the changes in depth of the surrounding waters. On both maps, numbers in black indicate measurements (in meters) taken before the eruption; numbers in red are depths after the event. Figure 2, in the area outlined in red, shows increased depths where the explosion has blown away the land underwater. Areas where depth has decreased, seen mainly in figure 4, show where volcanic matter has been deposited in sufficient volume to raise the level of the seabed.

The map in figure 3, based on an 1870 Dutch nautical chart, shows an updated view of the Sunda Strait, centered on the islands around the Krakatau volcano. Coastal areas colored red were flooded following the eruption, when the collapsing volcanic cone created a tsunami.

This map of the western part of the Indonesian archipelago shows the area where volcanic ash fell. Red numbers here indicate the depth in millimeters of the fallen ash.

Another dramatic visualization, figure 6 maps the global impact of the eruption, radiating out from the island of Krakatau. Numbers 1-12 are ships which were reached by falling ash; ships 13-18 reported spotting floating pumice stone, in one case as late as February 1884. The red circle marks the area where the explosion could be heard. Due to prevailing winds the sound was audible farther to the west than in other directions, thus a dotted line extends the circle past the island of Rodrigues. Including the western extension, the circle covers 1/14 of the earth’s surface.

Smaller areas enclosed by dotted lines represent ash falls associated with the eruption. The wavy lines radiating out all across the southern oceans show the progression of a massive wave, hour by hour, from Krakatau. The global impact of the eruption was yet broader, and lasted longer – the post on Headlines and Heroes describes how a volcanic ash cloud colored the skies for weeks as far away as Norway, and had sweeping climatic effects for years.

Dramatically showing the local impact of the eruption, figures 20-28 are maps of various affected areas of nearby islands. Orange-colored areas were flooded; within them you can spot villages, piers, wells, and a telegraph station, all destroyed by the waves resulting from the eruption. Figs. 27 and 28 compare the inundated city of Teloeq Betoeng – an area encompassed by the modern city of Bandar Lampung – in 1877 and after the eruption. Fig. 20, in the top left, shows Calmeyer Island, a temporary island formed from rocks and sediment discharged from the volcano, which eroded to nothingness within two years.

In this final set of maps, cross-sections and geological maps of the island show the dramatic changes before (figures 34, 35, 36, and 42) and after the eruption (figures 37 and 43). A dotted line outlines an ancient volcanic cone, which had been destroyed in an earlier eruption well before 1883.

These maps, produced more than 125 years ago, give us a direct visual of our volatile planet, in an area which continues to change dramatically. In 1927, further eruptions created a new island where Krakatau had once risen above the waves. It was dubbed Anak Krakatau – “Child of Krakatoa” – and is the site of continued volcanic activity, having erupted a 10,000-foot column of ash as recently as April 2022.