Krakatoa: Volcanic Island Morphology and Ecological Succession

This entry provides information on the physical attributes and biological recolonization processes observed in the Krakatoa Archipelago, specifically focusing on the primary island, Rakata, following the 1883 eruption.

Rakata's Post-Eruption Caldera Rim

The 1883 eruption significantly altered the Krakatoa islands. Rakata, originally the southernmost cone, was bisected, leaving a steep caldera wall facing the collapsed center. This remnant formed a cliff face of exposed volcanic rock, showcasing layers of ash, pumice, and solidified lava flows.

Volcanic Materials and Coastal Features

The coastlines consist of black volcanic sand and gravel derived from the erosion of the volcanic rock. Over time, wave action has sculpted shorelines and created beaches. Pumice rafts, initially abundant following the eruption, have largely disappeared, though fragments can still be found.

The Emergence of Anak Krakatau

A new volcanic cone, Anak Krakatau ("Child of Krakatoa"), emerged in the caldera beginning in 1927. This active volcano features a central cone, a crater, and lava flows, adding new landmass to the archipelago. Its form is constantly changing due to ongoing eruptions and collapses.

Vegetation and Ecological Succession

Recolonization of Krakatoa by plant life has been a subject of scientific study. Pioneer species, dispersed by wind and sea, established themselves on the sterile volcanic soil. A sequence of vegetation development has followed, progressing from grasses and herbs to shrubs and eventually trees.

Wildlife Recolonization

Animal life, including insects, birds, reptiles, and mammals, has gradually returned to the islands. Dispersal mechanisms include flight, ocean currents, and human introduction. The biodiversity of the islands continues to increase as ecological niches are filled.

Long-Term Morphological Changes

The shape and size of the islands in the Krakatoa Archipelago are subject to continuous alteration due to volcanic activity, erosion, and deposition. Coastlines recede and advance, and the elevation of volcanic cones changes with each eruption.