18-Jul-2018: Meghalayan Age: A new phase in the Earth’s history named after Meghalaya rock
Geologists have classified the last 4,200 years as being a distinct age in the story of our planet and named it the Meghalayan Age, the onset of which was marked by a mega-drought that crushed a number of civilizations worldwide. The International Chronostratigraphic Chart, the famous diagram depicting the timeline for Earth's history will be updated.
The Meghalayan, the youngest stage, runs from 4,200 years ago to the present. It began with a destructive drought, whose effects lasted two centuries, and severely disrupted civilizations in Egypt, Greece, Syria, Palestine, Mesopotamia, the Indus Valley, and the Yangtze River Valley. It was likely triggered by shifts in ocean and atmospheric circulation.
The Meghalayan Age is unique among the many intervals of the geologic timescale in that its beginning coincides with a global cultural event produced by a global climatic event.
To win a classification, a slice of geological time generally has to reflect something whose effects were global in extent, and be associated with a rock or sediment type that is clear and unambiguous.
For the famous boundary 66 million years ago that marks the switch in period from the Cretaceous to the Palaeogene, this "golden spike" is represented by traces in sediments of the element iridium. This was spread across the planet in the debris scattered by the asteroid that wiped out the dinosaurs.
For the Meghalayan, the spike is epitomised in a perturbation in the types, or isotopes, of oxygen atoms present in the layers of a stalagmite growing from the floor of Mawmluh Cave in the northeastern state of Meghalaya in India. This two-step change is a consequence of weakening monsoon conditions. The isotopic shift reflects a 20-30% decrease in monsoon rainfall.
The two most prominent shifts occur at about 4,300 and about 4,100 years before present, so the mid-point between the two would be 4,200 years before present, and this is the age that geologists attribute to the [Meghalayan golden spike].
The oceanic pole of inaccessibility is the place in the ocean that is farthest from land. It lies in the South Pacific Ocean, 2,688 km from the nearest lands.
Known as "Point Nemo", Nemo being Latin for "no one" and also a reference to Jules Verne's Captain Nemo, it lies more than 1,400 nm.(2,593 km) from the nearest landmass.
The area is so remote that sometimes the closest human beings are astronauts aboard the International Space Station when it passes overhead.
The area is also known as a "spacecraft cemetery" because hundreds of decommissioned satellites, space stations, and other spacecraft have been deposited there upon re-entering the atmosphere to lessen the risk of hitting inhabited locations or maritime traffic. Point Nemo is relatively lifeless; its location within the South Pacific Gyre blocks nutrients from reaching the area, and being so far from land it gets little nutrient run-off from coastal waters.
5-Feb-2018: Scientists find massive reserves of mercury hidden in permafrost
Researchers drilled a permafrost core on the North Slope of Alaska near Deadhorse and discovered that thawing permafrost in the Northern Hemisphere stores twice as much mercury as the rest of the planet’s soils, atmosphere, and oceans. The finding has significant implications for human health and ecosystems worldwide.
Scientists led a study to measure mercury concentrations in cores of frozen ground—or permafrost—from Alaska and used the data to estimate how much mercury has been trapped in Northern Hemisphere permafrost since the last Ice Age.
They found that Northern Hemisphere permafrost regions contain 1,656 gigagrams of mercury (32 million gallons, or enough to fill 50 Olympic-sized swimming pools), making them the largest known reservoir of mercury on the planet. This amount is nearly twice as much mercury as all soils outside of the northern permafrost region, the ocean, and the atmosphere combined.
The researchers also found that of the 1,656 gigagrams of mercury, 863 gigagrams lie in the surface layer of soil that freezes and thaws each year (27 Olympic-sized swimming pools), and 793 gigagrams are frozen in permafrost (23 Olympic-sized swimming pools).
Permafrost is permanently frozen ground and occurs in approximately 22.79 million square kilometers, or about 24 percent of the Northern Hemisphere land surface surrounding the Arctic ocean.
Mercury naturally occurs in the Earth’s crust and typically enters the atmosphere through volcanic eruptions. The element cycles between the atmosphere and ocean quickly. However, mercury deposited on land from the atmosphere binds with organic matter in plants. After the plants die, soil microbes eat the dead organic matter, releasing the mercury back into the atmosphere or water.
In permafrost regions, however, the organic matter gets buried by sediment before it decays and becomes frozen into permafrost. Once frozen, the decay of organic matter stops, and the mercury remains trapped for thousands of years unless liberated by permafrost thaw.
As long as the permafrost remains frozen, the mercury will stay trapped in the soil. Higher air temperatures due to climate change could thaw much of the existing permafrost, allowing the decay of organic matter to resume and releasing mercury that could affect Earth’s ecosystems. The released mercury can accumulate in aquatic and terrestrial food chains and cause harmful neurological and reproductive effects on animals.
The researchers intend to release another study modeling the release of mercury from permafrost due to climate change.