Tectonic tragedy: Balochistan earthquake

The science of Balochistan’s recent seismic activity and why it stays active.

On September 24, 2013 at around 4:30 pm, an earthquake that the United States Geological Survey clocked at 7.7 on the Richter scale jolted Awaran in Balochistan. The shocks are said to have been felt as far away as New Delhi. Upwards of 400 people have been reported to have died and thousands have become homeless just a few weeks before the harsh Baloch winter strikes. The toll continues to rise as damage is assessed.

Such calamities are, however, not new to the province. Quetta, the capital, was almost completely flattened in the 1935 quake and in 1945 there was another big one that destroyed buildings, killed people and resulted in a tsunami that brought devastation to the coastal belts. These events have become part of folklore. The recent quake has also given rise to its own mythical history in the making with the surprise creation of a mysterious island off the Gawadar coast.

A tale of two continents

So what makes Balochistan prone to such frequent and violent seismic activity? While its strategic location has been the subject of much political and social debate, the province is also interestingly situated tectonically. In order to understand the geography, we have to dive into some history or even pre-history.

Ninety million years ago, the Indian plate that carries the Indian subcontinent was drifting in the South Indian Ocean, off the coast of Africa and started to move up. It bumped into the Eurasian plate, forming the Karakoram and Himalaya ranges among others. SOURCE: RENDERED FROM PHD THESIS OF PIERRE DÈZES 1999; INSTITUT DE MINERALOGIE ET PETROGRAPHIE, UNIVERSITÉ DE LAUSANNE

The Hawai’ians believe that the crust of the Earth rides on a super gigantic marine turtle and as it moves, quakes are caused and volcanoes erupt. The truth is slightly different. The crust of the Earth is made up of “tectonic plates” that ride on the free-flowing inner core. These plates are not stationary but are in constant motion as the cracked surface of ice would be, floating on the surface of water in a container. The plates rub against each other and at the seams — geologists call them ‘plate boundaries’. There are roughly seven major and several minor plates that the Earth’s surface is divided into.



It is believed that, 90 million years ago, the Indian plate that carries the Indian subcontinent, was drifting somewhere in the South Indian Ocean, off the coast of Africa and started to move northwards (see map). Resultantly, the Indian Subcontinent, that looks like a triangular peninsula, bumped rather violently into the Eurasian plate and attached with it somewhere between 55 to 50 million years ago.

This map shows the location of the different plates and how they converge specifically in Pakistan’s terrain.

It took the triangular Indian Subcontinent between 35 and 40 million years to cover this journey of a few thousand kilometers, which might seem a little slow, but it is breakneck speed in tectonic time. And just as if two trucks hit each other head-on, the points where the plates collide, crumple upon impact. These ‘dents’ in the geographic realm are the mountainous terrains that we see all along the seam.

They start from the underwater ranges and coastal ridges of Makran and adjoining areas. The series of hills that Karachi sees rising from the coast near Cape Monze continue in some form or the other, changing names, directions and altitudes — the Kirthar range, Central Bruhui range, Sulaiman range and Salt range as they traverse the length of Pakistan.

A relief (or topographic) map of the subcontinent will reveal that the merging mountain ranges continue further into the Hindukush, the Karakoram and the Himalayan ranges — the big boys of Asia. The mountains run on across parts of Pakistan, China, India, Nepal and Bhutan before finally ebbing away into the sea once again near the Myanmar-Thailand border areas — all along the boundary of the Indian plate.

Three cockles and an ancient sea urchin all picked up on a visit to the Khirthar Range, formed when the Indian plate collided into the Eurasian plate millions of years ago.

So where did the bulk of the collision force go? The crumple zone of this collision proved to be Tibet, which became the rooftop of the world.

The Indian plate, being such a huge land mass, has a lot of inertia, which means that it has still not stopped moving and is till bumping into the Eurasian plate. This one is in slow-motion, though. As a result, the Tibetan plateau continues to rise and Mount Everest keeps getting taller, by approximately 4mm each year.

Tectonic plates cover the entire surface of the Earth, even the underwater sea floor is part of one plate or the other. Hence, at the time of collision, the colliding edge of both the land masses was the seabed; it is only natural that the seabed got crumpled the most. Amazingly, most of this crumpled seabed is what forms the mountains today! Thus, it comes as no surprise that explorers and mountaineers often find fossils of sea creatures embedded in rock from the Salt Range to areas near the Everest! My own humble forays into Kirthar have yielded a minor collection of fossilized sea creatures (see photo).

Three plates and a province

Balochistan, that forms the Western boundary of the Indian plate, is also absorbing immense pressure from the Arabian plate in the south that is “subducting” under the Eurasian plate in the Makran Subduction zone.

Simply put, subduction occurs when, in the case of two plates, a head-on collision and crumpling is avoided as one plate starts to creep or slip under the other. This movement does not, however, come without “some” crumpling and raises the chances of frequent seismic activity.

The seismic events caused by all the tectonic movements around Makran have been studied and researched, by one Charles Francis Richter, of the “Richter Scale” fame.

IMAGES: NASA EARTH OBSERVATORY

Perhaps the most fascinating geographic phenomenon of the recent seismic activity is the emergence of the island off Gawadar’s western bay. It emerged so suddenly that several fishes, including sting rays, were found on its surface. The creatures did not get enough time to escape as the mud volcano rose. The would have been discovered by the scores of curious fishermen and explorers scrambling over it as shown in the media. Some excited folks have even suggested it be turned into a resort.



This is not the first time something like this has appeared and it is unlikely to be the last. The first recorded case came after the 1945 quakes when three of these Atlantisis made an appearance near Malan, Balochistan. Then, there was the 1999 occurrence and one in 2010. Each time, though, the islands have disappeared over time, but perhaps not as suddenly as they arose.

SOURCE: RENDERED FROM THE ORIGINAL INCLUDED IN “AN OVERVIEW OF MUD VOLCANOES ASSOCIATED TO GAS HYDRATE SYSTEM” BY UMBERTA TINIVELLA AND MICHELA GIUSTINIANI.

Subduction (sliding under each other) sometimes creates layers of crystallized methane. Although Methane is a “gas”, under the right circumstances and pressure it turns into crystals called hydrates. The weight of a continental shelf near the subduction zones can perhaps exert the right kind of pressure for such a conversion to take place.

Pakistan has a considerable caché of Methane Hydrates near the Makran subduction zone. Not surprisingly, India has similar deposits near the Andaman islands, yet another subduction zone. Science is still working on how to harvest these resources in a stable manner without precipitating seismic activity or environmental catastrophes.

Nature’s mud slinging

Disturbed by seismic activity, pockets of gas around the hydrates often exploit an exposed weak spot and exert pressure for release. The results, on land, are mud volcanoes that look like regular or igneous volcanoes but spew mud, debris and gases instead of lava. When the same phenomenon occurs on the sea bed and the sea is shallow, as in the case of the Makran coastal areas, the resultant “mud volcano” often rises above the water surface, creating an island.

As the gases continuously release, the underground pressure subsides and wave action in the ocean, especially during the monsoons, weakens the mud island that crumbles until only a mound of rubble on the seafloor is all that is left of our Atlantis.



Our recent dot in the blue might take some time before disappearing though as it is located in very shallow water and is large in size. It will take time even though the elements which could erode it have a strong presence here; Gawadar is called the Gateway of Wind (“Gwad-dar” literally means Wind-door), and monsoon currents can be quite a force here.



Treasure and trouble

Mud volcanoes are only one of the many geological wonders of Balochistan which has large deposits of minerals and has seen many unusual phenomena emerge. The copper and gold deposits at Saindak and Rekodiq, the marble quarries of the south and the Sui field are some examples. However, they come at the high price of being prone to above-average seismic activity and hazards. In 2010, spewing lava from Tor Zawar mountain near Ziarat was one example.

And so, while Balochistan offers us a rich example of geological science at work, for now perhaps our attentions need to be immediately focused on rescue, relief and rehabilitation. Hundreds have died, thousands are homeless and the harsh winter is only a few weeks away.

The author can be reached at [e-mail]

Published in The Express Tribune, Sunday Magazine, October 6^th, 2013.