Category Science

What is trinitite?

On July 16, the US tested the world’s first atomic bomb in a New Mexico desert, near the town of Alamogordo. The test was nicknamed ‘Trinity’. The intense heat produced by the massive detonation instantly liquefied the sand. When it cooled down, the sand in the 730-m wide crater had turned into chunks of jade-green glass.

The glass was in strange forms – uneven marbles, knobbed sheets, thin valled bubbles and wormlike ribbons. Known as trinitite, atom site or Alamogordo glass, it was mildly radioactive but safe to handle.

After Hiroshima and Nagasaki, when nuclear bombs were no longer a secret, reporters were shown around the test site. They pocketed the bits of crater glass as souvenirs. Later, with the general public allows in for two days a year, the trinitite began to vanish. It showed up in souvenir shops and even as jewellery.

The army belatedly bulldozed the site in 1952 and made it illegal to collect the trinitite. However, the mineral is still traded online with collectors paying big sums for pieces which contain melted copper or iron from the site.

 

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How do they measure sea level?

Tide gauge is among the oldest methods to measure sea level. A tide gauge is fitted with sensors and placed on piers. It continuously records the height of the surrounding water level. Water older tide-measuring stations used mechanical floats and recorders, modern monitoring stations use advanced acoustics and electronics. Sea level is also measured from space using laser altimeters, which determine the height of the sea surface by measuring the return speed and intensity of a laser pulse directed at the ocean. The higher the sea level, the faster and stronger the return signal is.

You can see that getting an accurate reading (for example, down to the millimeter level) is extremely difficult. Satellites are now used as well, but they suffer from many of the same problems. Scientists do the best they can, using extremely long time spans, to try to figure out what the sea level is and whether or not it is rising. The general consensus seems to be that the oceans rise about 2 millimeters per year.

 

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What are the impacts of sea-level rise on coastal region?

  • The impact of sea-level rise includes flooding, habitat destruction and salt water intrusion in coastal areas, increased soil erosion and disappearance of low-lying islands. Rising sea levels also make storm surges capable of much greater damage. (Storm surge is the abnormal rise in seawater level during a storm. Storm surge can penetrate well inland.)
  • Higher sea levels are coinciding with more hurricanes, contributing to more powerful storm surges that can strip away everything in their path.
  • Saltwater intrusion is the flow of seawater into water bodies such as rivers and aquifers (underground water bearing rocks). It is a major concern as it can induce contamination of water resources, used for drinking, household purposes and agriculture. Increased salinity of coastal freshwater can threaten vegetation and wildlife of the region.
  • Many birds use coastal ecosystems to find food, live and breed. Sea turtles lay their eggs on beaches, returning to the same location every year. When beaches erode, these animals and birds will be affected.
  • Rising sea level will lead to the displacements of people. It could create 187 million climate refugees by 2100, according to a study.

 

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What are the two primary factors of sea-level rise?

The rise in sea-levels is linked to two primary factors, both induced by global warming.

Thermal expansion:

The oceans are absorbing more than 90% of the increased atmospheric heat associated with greenhouse gas emissions. When water heats up, it expands. The ocean water expands to fill a greater volume and takes up more space. This is called thermal expansion, and it is responsible for one-third of the sea-level rise, according to studies.

Melting of glaciers and ice caps:

Warmer temperatures cause land-based ice such as glaciers and ice sheets to melt, and the meltwater flows into the ocean to increase sea level. Melting ice causes about two-thirds of the rise in sea level.

If all the ice in glaciers and sheets melt then the sea level would rise by 216 feet. That could cause some countries to disappear under the oceans. That’s a scenario scientists think would probably take many centuries, but it could eventually happen if the world keeps burning fossil fuels indiscriminately.

 

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What causes sea-level rise?

A rise in sea level may put some of the Indian cities, including Mumbai, Chennai and Kolkata, in the flood-risk zone, and it could affect a total of 36 million people in the country by 2050, according to a research report by the New Jersey-based science organisation Climate Central. By 2100, this number could increase to 51 million. Parts of these coastal cities could be completely wiped out, the report said.

Showing that many of the world’s coastlines are now for lower than earlier, the report projected that worldwide, some 300 million people could be affected by 2050. The threat is particularly concentrated in six Asian countries: China, India, Vietnam, Thailand, Indonesia and Bangladesh.

Sea-level rise and flooding could have profound economic and political consequences within the lifetimes of people alive today, showed the findings of the study.

Even if emission is zero

According to another study published last month, the dramatic rise in sea levels will continue even if the world manages to slash greenhouse gas emissions to zero by 2030. Emissions between 2015 and 2030 would be enough to raise levels by 8 cm by 2100, according to research by experts based in Germany.

The average sea level is expected to swell by at least a metre by 2300 in the extremely unlikely event that greenhouse gas emissions fall to zero in the next 11 years.

If planets heats up further

In the worst-case scenario – in which the planet heats up by 5 degrees Celsius in the next 80 years – melted ice could raise sea levels worldwide by more than 6.5 feet, according to a study published in May 2019. That could result in a loss of 6,91,120 square miles of land, the report said. That’s an area larger than France, Germany, Spain and the U.K. combined.

The water could swamp major coastal cities such as New York and Shanghai. Small Pacific island nations such as Vanuatu would be rendered uninhabitable or disappear entirely.

In Earth’s geological past, sea level has risen and fallen dramatically. For instance, during the last Ice Age, ice covered the planet and sea level was at least 394 ft lower than what it is today. And during the Eocene – 40 million years ago, the Earth was almost ice-free and the sea level was around 230 ft higher than today.

These changes are part of Earth’s natural glacial cycles and have occurred over millions of years. But the current sea-level rise is caused mainly due to human activities.

The burning of fossil fuels, deforestation, decomposition of waste in landfills and livestock have released enormous amounts of greenhouse gases into the atmosphere. These emissions have caused the Earth’s surface temperature to rise, causing global warming, which directly contribute to sea-level rise.

 

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WHEN DOES THE WIND START TO DAMAGE BUILDINGS?

          Damage to buildings during a storm obviously varies according to the construction and location of the building, but damage generally occurs above Force 9 or 10. Chimney pots, roofing tiles and slates are the parts of buildings most at risk from storm damage.

          As wind passes over and around a building, two things happen.  First, positive wind pressure applies to building components on the side(s) of the building that face the incoming wind (the “windward” direction).  The windward wind load is essentially the force of the blowing wind pressing on the building.  Second, negative wind pressure applies to building components on the side(s) of the building that face away from the incoming wind (the “leeward” direction).  The negative wind pressure is also known as “suction.”  The suction force will be applied to vertical surfaces such as walls, and also horizontal or sloped surfaces such as roofs.  The suction force can be thought of as acting like a vacuum that pulls on a building and its components.

          During an event with moderately strong winds, building materials such as asphalt shingles or vinyl siding may displace away from the building.  Sometimes, windows break and the broken shards end up outside of the building.  In such cases, a common misconception held by many people in the construction industry is that wind must have gotten under or behind the surface of the material to “blow” it out.  However, acknowledging and understanding the concept of wind suction can explain how those materials were damaged.  Wind does not only apply a direct blowing force on buildings, but it also induces a suction force.  Depending on various factors, the suction force can be significant enough to cause damage to individual building components or the structure of the building itself.

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