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:

Shoelace fanatic

Thanks Andrew for this wee gem, if gem is the word I want...Ian's shoelace site shows you the many options available to you when lacing your shoes.

It also details why there are almost 2 trillion possible ways of lacing a 12-eyelet boot.

And there are some very pretty lacing patterns: check out the hexagram and pentagram, just for starters.

And for those among us who struggle with the basics, there is help to avoid slipping knots and crooked bows!

What a wonderful site. :-)