Earth Time

Some Geography of Recent Times

 

The meanings of geographical terms we recently noticed in news.

The human population is increasing at such a rate that the earth is no longer capable of bearing the extraordinary consumption pattern of humans. The pressure so exerted on the earth is catalysing catastrophic changes, which hits back humans, like global warming and climate change. The least developed and developing economies of the world are the worst affected ones. 

Some geographic terms, which are new to us and are in one or the other way, making an impact on our daily life are being discussed here. The context is nothing but the over exploitation of natural resources.

SOIL PIPING

When water erodes the layer beneath the surface of the ground and creating underground tunnels we call it Soil Pipe. This usually begins as small pores underground and are enlarged with increase erosion, in some instance these hole may be even large enough for a person to crawl through.

 

In areas where there are cracks in the soil present, or less resistance to erosion, presence of ground opening when trees are uprooted, holes created by animals etc can result in soil piping as water passes through them. River banks are prone to this phenomena.

HUNGRY WATER

The widespread damage caused by the 2018 floods in Kerala can be attributed to the ‘hungry water’ effect caused by the surge of sediment-starved water from the upstream reaches of a river.

Dams and reservoirs trap the sediments eroded from rocks and soils, leaving the river starved of its sediment load. This starved river water will be having high amount of potential energy. Thus gained potential energy of the hungry water released from dams will scour the river banks downstream, uprooting trees or riparian vegetation and damaging bridges and other engineering structures.

CORAL BLEACHING

Normally, coral polyps live in an endosymbiotic relationship with algae called Zooxanthellae, crucial for the health of the coral and the reef. The coral - the cluster of shells made of Calcium Carbonate, by a microorganism known as coral polyps. They provide shelter for Zooxanthellae. Coral bleaching occurs when coral polyps expel algae that live inside their tissues. 

The algae provides up to 90 percent of the coral's energy in return to the service provided by it. Bleached corals continue to live but begin to starve after bleaching. Some corals recover.

The leading cause of coral bleaching are rising water temperatures, clogging and siltation of water, pH variation of water, pollution of various kinds, bottom trolling, anthropogenic activities etc.

ENSO

ENSO elaborates to El-Nino and Southern Oscillations, which is a group of phenomenon associated with the ocean water temperatures and the atmospheric air circulation in the central and eastern tropical Pacific ocean. On periods ranging from 3 to 7 years waters of the tropical Pacific ocean undergo warming or cooling of about 1°C to 3°C.

ENSO occurrence directly affects rainfall distribution in the tropics and can have a strong influence on weather across the United States and other parts of the world. El Niño and La Niña are extreme phases of the ENSO cycle; between these two phases is a third phase called ENSO-neutral.

El-Nino

A warming of the ocean surface, or above-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to become reduced while rainfall increases over the central and eastern tropical Pacific Ocean. The low-level surface winds, which normally blow from east to west along the equator (“easterly winds”), instead weaken or, in some cases, start blowing the other direction (from west to east or “westerly winds”).  In general, the warmer the ocean temperature anomalies, the stronger the El Niño (and vice-versa).

La-Nina

A cooling of the ocean surface, or below-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to increase while rainfall decreases over the central and eastern tropical Pacific Ocean. The normal easterly winds along the equator become even stronger.  In general, the cooler the ocean temperature anomalies, the stronger the La Niña (and vice-versa).

Neutral

Neither El Niño or La Niña. Often tropical Pacific SSTs are generally close to average.  However, there are some instances when the ocean can look like it is in an El Niño or La Niña state, but the atmosphere is not playing along (or vice versa).

CLOUD BURST

A cloudburst is an extreme amount of precipitation in a short period of time, sometimes accompanied by hail and thunder, which is capable of creating flood conditions. A cloudburst can suddenly dump large amounts of water e.g. 25 mm of precipitation. 

 

However, cloudbursts are infrequent as they occur only via orographic lift (pushing of clouds by hindrances in their paths such as hills or mountains. Eg: Western Ghats in Kerala) or occasionally when a warm air parcel mixes with cooler air, resulting in sudden condensation. At times, a large amount of runoff from higher elevations is mistakenly conflated with a cloudburst.

LANDSLIDE

A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity. 

 

Usually cloudburst can result in landslides in ecologically sensitive slopes. As the long duration rainfall can cause loss of binding between the surface soil and the bedrock of slopes.

Did we miss something?? 

APPENDIX

Dept of Risk and Disaster Management

The Hindu

National Weather Service

usgs