Extremely scary jobs

"The hazardous career field of commercial diving was once largely defined by the deep-water saturation divers working the oil rigs in the Gulf of Mexico and the North Sea. But saturation diving isn't the only dangerous diving job around. Someone has to dive the 150-foot-tall water towers on the blizzard-blown Kansas prairies where it's gravity, not gas saturation, that will kill you. Someone needs to slip quietly inside the tangled gloom of a tuna net to check on great white sharks. Someone needs to make sure those scientists chasing penguins under the Antarctic ice cap don't drift away from the hole. And yes, someone has to dive inside nuclear reactors. (But hey, we hear the tan you get is just fabulous.)"

Read the whole article here. It's fascinating, but could give you nightmares!

Thanks to the NZ Geographic for this link.

A lot of scary amazingness

65 million years ago, a meteor at least 10-km wide impacted Mexico's Yucatan Peninsula, causing global catastrophe.  The force of the explosion was significantly bigger than any volcanic event in history and the shock waves probably triggered worldwide earthquakes, a megatsunami, a massive release of gas and dust and heating of the atmosphere which devastated the climate and caused mass extinctions, including most dinosaur species existing at that time.

The site of the impact, Chicxulub crater; is a circle 170km across, with half on the Yucatan Peninsula, and the other half in the water of the Caribbean Sea.

On land, a trough along the outer edge of the crater contains a vast semicircle of "cenotes", deep limestone sinkholes filled with fresh water.


This BBC clip explains:





Many of the cenotes are connected by an even deeper network of flooded caves which leads to the sea.  Freshwater percolating down from rain on the surface and seawater flowing in from the Caribbean form "haloclines", distinct layers of water which don't mix.  This clip shows the strange optical illusions caused at the boundary between the layers:

The first half of this clip shows another peculiar optical effect: a layer of hydrogen sulphide which appears to be the bottom of a cenote but is in fact a cloud of gas suspended deep below the surface: