Disasters shaping the Lands we Live On

Figure: Tohoku Earthquake of Japan

Earth holds the record of all violent things it has gone through. Disasters do not occur in a normally tranquil planet; rather, they are geologic chapters. Valleys are raised by earthquakes, islands are formed by volcanoes, shorelines are redrawn by tsunamis, and mountainsides are cut along landslides. These abrupt breaks, which have been piled up over millions of years, are what have formed the landscapes that we recognize nowadays. Learning to appreciate the beauty of this Earth is to learn its catastrophes. 

One of the strongest sculptors is Earthquakes. The 2004 Sumatra-Andaman earthquake has pushed sections of the seafloor several meters up, affecting the Indian Ocean tsunami, which has permanently changed the coastline from Indonesia to Sri Lanka. Entire fishing communities were found inland, as new sandbars were created; other areas were washed away and disappeared beneath the sea. 

The Tohoku earthquake that took place in Japan in 2011 changed the landscape in a way that continues to surprise scientists. At the time of the magnitude-9.0 megathrust quake of 11 March 2011, the Pacific Plate darted violently under the North American Plate, generating hundreds of years of built-up pressure within hundreds of seconds. One of the greatest lateral movements recorded by continuous GPS stations throughout Japan was the eastward movement of the island of Honshu by approximately 2.4 meters: an enormous motion of a landmass of that mass. The Geospatial Information Authority of Japan and the US Geological Survey studies indicate that the offshore fault ripped apart in more than 400 kilometers, and some subsections of the Pacific coast of Japan have slipped by 50 to 60 meters—the type of movement that is normally accrued over hundreds of years. a post-2011 outline on the Pacific coast of Japan is substantially different than the pre-quake outline. These are not scars of the landscape but geophysical revisions—changes in elevation, changing river mouths, new basins, and reorganized ecosystems. A lot of the subsidence and coastline change, as studies by the University of Tokyo and the USGS have pointed out, will last centuries, and so the 2011 Tohoku event is not just a disaster on human account but the significant event in the geological record of modern Japan. 

Figure: Changed Landscape of the Himalayas due to the Gorkha earthquake of Nepal

The 2015 Gorkha earthquake in Nepal changed the Himalayan landscape, which was both sudden and deep. When the magnitude-7.8 earthquake happened on 25 April 2015, one of the strongest tectonic boundaries on Earth, the Main Himalayan Thrust, slipped forward as the Indian Plate in its eternal motion pushed into Eurasia. According to the NASA and ESA satellite interferometry in high resolution, Kathmandu Valley lifted about 1 meter, which was an uplift due to the crust shrinking upwards as the fault moved. Simultaneously, regions northwards, such as portions of Langtang and the upper Himalayas, moved by over half a meter, showing that just one rupture is enough to roll a region of the Earth. These vertical movements altered the behavior of water in central Nepal almost instantly. Rivers like the Bagmati and Bishnumati started to be a little slower or faster, and the erosion increased in some of the channels and decreased in others. Some ground that previously had drained freely was now worse than before, exposed to waterlogging, and little lakes and depressions were formed where the ground had been drawn down. Landslide forms developed as well with a great deal of difference: the new topography and low storm and slopes caused thousands of slides in the weeks and months that followed, moving the valleys, damming streams, and forming temporary lakes, which eventually burst and redistributed downstream channels. The Gorkha earthquake was particularly instructive about how the long-established geomorphology was rewritten in a very short period. Hundred-year-old landforms, terraces, ridgelines, and river bends were rearranged in less than a minute. 

Volcanic eruptions are more dramatic. When they explode, they create new worlds altogether. Among the most renowned in history is Mount Vesuvius. When it erupted in 79 CE, it did not only cover Pompeii and Herculaneum; it also changed the whole Bay of Naples. The coastline was filled with pyroclastic flows, which pushed the land outwards by several hundred meters in certain locations. In some measure, the form of the coastline that we see today is the product of that eruption. The Roman towns became layers of lava, and the area was reshaped in several hours thanks to Vesuvius. 

The eruption of Mount St. Helens that occurred in 1980 is one of the best examples of the possible eruption of a volcano that may redesign an entire landscape within several minutes. Following weeks of earthquake-related rumbling and a swelling of its northern flank, on 18 May 1980, the volcano had a magnitude-5.1 earthquake, which caused a major slope failure. It was not a landslide—that was the greatest avalanche of debris of all time. Among the most dramatic outcomes came the formation of the new location and elevation of Spirit Lake: the landslide pushed the lake northwards and elevated its surface almost 60 meters. The debris blocked the small valleys, creating entirely new hydrological systems that had never existed before 1980, flattening or covering over entire forests with ash, and depositing entirely new volcanic soils. Mudflows (lahars) of mud with high amounts of sediment swept over river valleys, creating new channels and rocky layers of tectonic material over the Washington State landscape. 

Even underwater volcanoes have the potential to rewrite the map in a very fast fashion, and the Tonga eruption of 2015 is one of the brightest ones in recent history. In December 2014, a submarine vent with a two-mile (3,200 m) inter-island depth started to erupt explosively, blowing ash, steam, and crushed rock thousands of meters into the atmosphere. The Smithsonian Global Volcanism Program and NASA Earth Observatory summarize that due to the eruption, a new landmass was formed through a process referred to as the "tuff cone formation," in which ash particles coalesce to form rock. During these few weeks the vent accumulated such material as to form an island all by itself—and ultimately, by joining the two older islands, a continuous landform more than 1.8 kilometers in length. But the history of the island had its dramatic conclusion. In January 2022, a mega Fluxus-level atmospheric eruption, the biggest in the atmosphere since Krakatoa in 1883, destroyed most of the Hunga Tonga-Hunga Ha'apai landmass. The volcanic cone was dispersed, and ash was thrown up 55 kilometers into the stratosphere by the eruption, and a wave of shock was felt around the planet. What was left was an extremely modified seabed, a recalibrated caldera, and little parts of what had been a growing island. 

The metamorphosis of Kilimanjaro is not as dramatic; rather, it is quieter and gradual and marked by volcanic bursts, volcanic crashes, and volcanic ice. The mountain consists of three old volcanic cones, Kibo, Mawenzi, and Shira, two of which have already been dislodged to form wide eroded mounds. Its steep valleys and jagged ridges were over hundreds of thousands of years sculpted by lava flows, flank failures, and landslides to provide the mountain with its broken skyline. Deeper gullies were then cut by the glaciers, and the rock was hewn out into sharp cirques and high, bare walls. A shrinking ice cap of Kilimanjaro is another change today. The ice is melting much faster than it was imagined, and as it passes, it exposes new rock and changes the seasonal water cycle, and inch by inch, it changes the face of the mountain. The history of its formation does not involve a volcanic eruption as other volcanoes do; however, Kilimanjaro remains a constant reminder that scenery can alter in great ways both by gradual, cumulative forces and by abrupt ones. 

These narratives bring to light the fact that the catastrophes on earth are part of the design. Earthquakes cause some land to be raised up and some to sink into the ground. Cities are buried by volcanoes, and new mountains, islands, and soils are formed. Tidal waves destroy the shoreline and create others. Landslides carve valleys. Glaciers are melting away due to climatic changes that have shaped mountains such as Kilimanjaro. The continents may also sink or emerge, as the destiny of Zealandia demonstrates. 

Earth is a restless artist. Its canvas is never finished. All mountain ridges, lava fields, canyons, deltas, and coastlines testify to the former turmoil. Whenever we gaze out upon a landscape, at the snow-white mountains of Kilimanjaro, at the precipices of the seacoast of Chile, or at the black lava flows of Hawaii, we are gazing on the ruins of millions of catastrophes that have made the world new. Knowledge of these forces assists us in realizing our own position on a planet that is constantly, noiselessly, or violently altering its form.