Sinkholes

This astonishingly unnerving photograph was posted today on the Flickr.com feed of the Guatemalan goverment and shows a seemingly bottomless sinkhole that opened up on Sunday in Guatemala City as a swath of Central America was drenched by tropical storm Agatha. Click here for the high-resolution version, if you dare. The storm only briefly hit tropical storm strength on Saturday as it came ashore from the Pacific Ocean over the weekend, but the  death toll had risen to 115 at last count. Here's a street-level view.

[via Sinkhole in Guatemala City - Dot Earth Blog - NYTimes.com]

[image courtesy of Sinkholes - Southwest Florida Water Management District Headquarters]

Collapse sinkholes happen suddenly where the overburden is thick with soils and heavy clay. Collapse sinkholes are deep, steeply-sided holes in the ground. They are frequently triggered by fluctuations in the water-table. As water levels fluctuate, the roof of the cavity is stressed and weakened. When the water-table drops too far, the cavity walls are unsupported and the ceiling becomes too weak to hold the heavy overburden. Eventually, the ceiling collapses and a sinkhole is formed. A conical debris mound left on the sinkhole floor is all that remains of the cavity ceiling.

[via Florida Sinkholes - Your Guide]

[image courtesy of Arbuckle Karst Conservancy]

Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite.

Due to subterranean drainage, there may be very limited surface water, even to the absence of all rivers and lakes. Many karst regions display distinctive surface features, with sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by a superimposed non-soluble rock strata. Some karst regions include thousands of caves, even though evidence of caves that are big enough for human exploration is not a required characteristic of karst.

Various karst landforms have been found on all continents except Antarctica (see: Notable karst areas).

[via Karst topography - Wikipedia]

let me tell you of the day we went to playa del carmen. we rented a yellow jeep and first drove to the cenotes accross the street (even though the car rental guy said they weren't the best and suggested other ones-but they were too expensive and touristy to go to). i couldn't wait to get to the cenotes, that's all i had talked about since i heard about them, cenotes, cenotes, cenotes. we arrived at the kantun-chi cenote park, it was sketchy to say the least. driving down a dirt road that passed abandoned buildings to a hut in the jungle we were a bit skeptical. but the people were really friendly, spoke no english, and there were other turistas so all seemed well.

we ventured to the first of 4 cenotes. it was a dark cave with freezing water. there were bottom feeding fish that would nibble your toes if you stood in one place too long and god knows what else in the deep, dark, depths. that's when i decided no snorkeling for me-i didn't want to see what i'd be swimming with. jim was more daring.

i finally got in the water, keeping my feet near the surface so nothing would snack on them, and swam around a bit. we then noticed the birds living on the ceiling of the cave. cute? not since their droppings had nowhere to go but in the water. and that's when we realized how stagnant the water was. so here we are, in the mexican jungle, swimming in stagnant water with bird crap. i jumped out. headed for the next cenote.

on the way it got a bit buggy. there was a monkey in the trees. it was on a leash with a big collar 'round its neck. odd. smoke everywhere-i'm not sure if it was to keep the bugs at bay, but it really wasn't working. i was covered in mosquitoes. i've never had so many on me at once. and that's when i freaked out. i had to get out of there. screw the cenotes. i nearly ran down the road to our jeep. upon returning the snorkeling equipment we were invited to come back to see the rest of the cenotes. sure-we'll be back later.

we actually went back to the resort, jumped in the pool-we figured the chlorine must have some disinfecting properties, took hot showers, drank to forget, brushed our teeth... it was as if we just couldn't get the cenotes off us. from that point on-they were referred to as no-notes.

More about our awesome honeymoon in the Riviera Maya

The deep sinkhole of Blue Hole Natural Monument in Lighthouse Reef Photographic Print

Approximately 60 miles (100 kilometers) from Belize City, the almost perfectly circular Blue Hole is more than 1,000 feet (305 meters) across and some 400 feet (123 meters) deep.

The hole is the opening to what was a dry cave system during the Ice Age. When the ice melted and the sea level rose, the caves were flooded, creating what is now a magnet for intrepid divers. Today the Blue Hole is famed for its sponges, barracuda, corals, angelfish-and a school of sharks often seen patrolling the hole's edge.

[via Belize, Blue Hole, Lighthouse Reef, Photo of the Day, Picture, Photography, Wallpapers - National Geographic]