Exam Topper

Mantle plume is an up-welling of abnormally hot rock within the earth’s mantle which carries heat upward in narrow, rising columns, driven by heat exchange across the core-mantle boundary. Eventually, the rising column of hot rock reaches the base of the lithosphere, where it spreads out, forming a mushroom-shaped cap to the plume.  Geophysicist, W. Jason Morgan, developed the hypothesis of mantle plumes in 1971. The largest (and most persistent) mantle plumes are presumed to form where a large volume of mantle rock is heated at the core-mantle boundary, about 1800 miles below the surface, although smaller plumes may originate elsewhere within the mantle. Heat transferred from the plume raises the temperature in the lower lithosphere to above melting point, and forms magma chambers that feed volcanoes at the surface.  Role of Mantle Plume in Plate Tectonics :  •Mantle plumes transport primordial mantle material from below the zone of active convection; produce time-p...

“Prevention is better than cure” is the motto of disaster management strategists around the world. The first step i.e. disaster preparedness embodies half of the disaster management planning process. Better preparedness against disaster checks the excess loss of life and property and thus, saves the revenues of the government to a greater extent.  Hazard Zone Mapping is an efficient measure to check disaster loss to a greater extent by micro-management of the different disaster-prone zones. It considers a particular disaster, such as earthquake and map it according to its severity and impact in different areas.  Landslide hazard zone mapping and its use in disaster management process.  • Landslide hazard zone mapping at regional level of a large area provides a broad trend of potential landslide zones. A macro level landslide hazard zone for a small area may provide a better insight into the landslide hazards.  • The hazard zone map produced by using techniques, such...

Dead zones are low-oxygen, or hypoxic, areas in the world’s oceans and lakes. Because most organisms need oxygen to live, few organisms can survive in hypoxic conditions. That is way these areas are called dead zones. Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. One of the largest dead zones forms in the Gulf of Mexico every spring. Hypoxic zones can occur naturally but climate change, nutrients run-off from the land, and eutrophication are leading to algal bloom and causing further depletion of oxygen level in water. As a result dead zones are spreading at much faster pace.  Consequences of spreading of Dead Zones on Marine Ecosystem  •The reduced dissolved oxygen in ocean water results in loss of marine life thus the habitats which were once teeming with life are transformed into biological deserts.  •Elevated nutrient levels and algal blooms can also cause problems in drinking water ...

1. Physical Vulnerability may be determined by aspects, such as population density levels, remoteness of a settlement, the site, design and materials used for critical infrastructure and for housing (UNISDR).  Example: Wooden homes are less likely to collapse in an earthquake, but are more vulnerable to fire. 2. Social Vulnerability: Refers to the inability of people, organizations and societies to withstand adverse impacts to hazards due to characteristics inherent in social interactions, institutions and systems of cultural values. It is linked to the level of well-being of individuals, communities and society. It includes aspects related to levels of literacy and education, the existence of peace and security, access to basic human rights, systems of good governance, social equity, positive traditional values, customs and ideological beliefs and overall collective organizational systems (UNISDR). In a disaster, women in general may be affected differently from men because of th...

United Nations Environment Programme (UNEP) has released a report, ‘Sand and Sustainability: Finding new solutions for environmental governance of global sand resources’, that highlights the problem of sand being extracted at rates exceeding natural replenishment rates. Coastal sand mining poses one of the biggest threats to our environment:  •While 85% to 90% of global sand demand is met from quarries, and sand and gravel pits, 10% to 15% extracted from rivers and seashores is a severe concern due to the environmental and social impacts.  •Their extraction often results in river and coastal erosion and threats to freshwater and marine fisheries and aquatic ecosystems, instability of river banks leading to increased flooding, and lowering of groundwater levels.  •The UNEP report notes that China and India head the list of critical hotspots for sand extraction impacts in rivers, lakes and coastlines.  •As per the report, most large rivers of the world have lost betwee...

Its physical characteristics like temperature, salinity, density and the external forces like the sun, the moon and the winds influence the movement of ocean water. Ocean currents are the continuous flow of huge amount of water in a definite direction. Water moves ahead from one place to another place through ocean currents. Ocean currents have direct impact on the climate and economy of the region.  Ocean currents and water masses differ in their impacts on marine life and the coastal environment in different ways:  • Impact on biodiversity:  The physical parameters of water masses are essential because they structure the water masses and determine the various habitats that provide the environmental conditions required for marine life.  These conditions influence the production and the growth of plankton and fish species. The dispersion and dwelling of larvae for many benthic and pelagic species depend on hydro-graphical factors. They also play an important role for...

Mountains are an important source of water, energy and biological diversity. Furthermore, they are a source of key resources such as minerals, forest products and agricultural products and of recreation. As a major ecosystem representing the complex and interrelated ecology of our planet, mountain environments are essential to the survival of the global ecosystem. Mountain ecosystems are, however, rapidly changing.  Developmental initiatives and Tourism in Mountains Adverse Impact:  • Dams and Roads: Dams and roads can be hazardous, if they are not properly constructed and managed. Disasters in mountains, and the forces that trigger them, affect larger areas, sometimes entire watersheds or river systems.  • Mining: The forces that shaped the world’s mountains also made them rich in minerals and metals, including gold, copper, iron, silver and zinc. Owing to increasing demand, mines are now being opened even in remote mountain areas, particularly in developing countries....

Mangrove forests form a unique wetland ecosystem, inhabiting the edge of land and sea, thriving in seawater. Over the past four decades, 35% of global mangrove forests have been destroyed. This degradation of mangrove forests has a knock-on effect on some of the world’s most endangered species which rely on them for habitat, such as the proboscis monkey and the Bengal tiger.  Causes of depletion of mangroves  The natural causes  • Cyclones, typhoons and strong wave action, especially in the geographically vulnerable Andaman and Nicobar Islands;  • Browsing and trampling by wildlife (e.g. deer) and livestock (goats, buffaloes and cows), which are often left to graze freely, especially in the areas close to human habitation;  • Damage by oysters to the young leaves and plumules of Rhizophora and Ceriops plants; crabs, which attack young seedlings, girdle the root collars and eat the fleshy tissues of the propagules  • Insect pests, such as wood borers, caterp...

Destruction of coral reef can be induced by a variety of factors, alone or in combination. However, unprecedented global warming and climate change combined with growing local pressures have resulted in destruction of coral reefs to a large extent.  Impact of global warming on the coral life system:  Coral Bleaching  • The impacts from coral bleaching are becoming global in scale, and are increasing in frequency and intensity.  • Mass coral bleaching generally happen, when temperatures around coral reefs exceed 1 degree Celsius above an area’s historical norm for four or more weeks. Sea surface temperature increases have been strongly associated with El Nino weather patterns. • However, light intensity, (during doldrums, i.e. flat calm conditions), also plays a critical role in triggering the bleaching response. If temperatures climb to more than 20 C for similar or longer periods, coral moralities following bleaching increase.  Rising sea levels  • Observa...