This Day in History (26-Jul-2005) – Mumbai receives 99.5cm of rain within 24 hours, bringing the city to a halt for over 2 days

On 26 July 2005, around 2:00 p.m. the Mumbai Metropolitan Region was struck with a heavy storm. The Indian Meteorological Department station in Santacruz had recorded a record 944 mm. of rain for the 24 hours ended at 08:30 a.m. on 27 July (eighth heaviest ever recorded 24-hour rainfall ).  Local train movement came to a halt by 2:30 p.m. due to the water logging on the tracks, due to which, vehicular traffic intensity on roads increased. Water logging and submergence of certain low lying pockets of the region such as Dharavi, Bandra-Kurla Complex, Chunabhatti, Chembur, Ghatkopar, Milan Subway and Sion either slowed down traffic, or brought it to a grinding halt.

The situation worsened when the cellphone networks went down around 5 p.m. Land-lines of M.T.N.L. were also only partially functional. Adding to the chaos was the lack of public information. Radio stations and many television stations did not receive any weather warnings or alerts by the civic agencies.  The Powai Lake had started overflowing at 4 p.m. and discharged 5.95 million cubic meters of water into the Mithi River. The rainfall hydrographs of 26 & 27 July later revealed that two flood waves were generated in the streams and river basins of Mumbai, one between 2:30 & 20.30 p.m.- coinciding with the high tide period and another between 8 and 10 p.m. Normally, the second wave would have harmlessly drained because of the prevalent low-tide. But that did not happen because the accumulated water from the first flood wave had yet not flushed out effectively during the ebb period because of a choked drainage system. The result was that the flood situation kept on aggravating throughout the night. There was some relief in sight only when the second ebb period commenced at 6 p.m. on 28 July.

Due to submergence of the power stations and substations, Suburban power supply was suspended from the evening of 26 July and it was restored only after the flood waters receded. As many as 5,000 people were killed in the floods across the state of Maharashtra, many of them in Mumbai



This Day in History (10-Apr-1815) – Mount Tambora in Indonesia Begins Erupting

Six hundred miles east of Jakarta, the capital of Indonesia, Mount Tambora stretches nearly 9,000 feet above the Java Sea on the island of Sumbawa. The volcano originally grew to about 12,000 feet elevation before a major explosion destroyed its summit and left a pre-1815 caldera more than 43,000 years ago. On April 10, 1815 evening, the towering peak exploded violently, killing more than 100,000 people, directly and indirectly, as it spewed rock and ash high into the atmosphere. The eruption, lasting more than three months, is the largest in past 10,000 years and, arguably, the most influential on a global scale.

The eruption emptied about 50-150 cubic km of magma and measures 7 on the VEI scale. It produced a giant plinian eruption column, which is estimated to have reached more 40-50 km altitude, ejecting large amounts of ash and aerosols into the stratosphere. With the cataclysmic eruption, the entire shape of the mountain changed. The caldera — the central peak — collapsed into the magma chamber below, decreasing the height of Mount Tambora by more than 5,000 feet as ash and rock shot up from below. Caldera collapse destroyed 30 km3 of the mountain and formed a 6 km wide and 1250 m deep caldera. Floating islands of pumice 3 miles long were observed in April 1815, and even 4 years later, these islands still hindered navigation.  As the intense heat escaped through the vent, the explosion was heard some 1,600 miles away in western Indonesia.

Up until the summer of 1816, with ash still in the upper atmosphere, the long-term consequences of the eruption finally began to take shape, causing the “Year Without a Summer” and wreaking havoc on weather patterns. The reason for the climatic changes was increased absorption of sunlight due to a veil of aerosols (consisting mostly of tiny droplets of H2SO3 acid, formed by SO2 release) that were dispersed around both hemispheres by stratospheric currents from the tall eruption column.  Global temperatures dropped by as much as 3 deg C in 1816 and recovered during the following years.