The Earth Story

Great Blue Hole sheds light on Maya collapse

Located off the coast of Belize in an idyllic coral reef, the blue hole is part of a karst limestone landscape that was flooded by sea level rise at the end of the last ice age (see http://on.fb.me/1KbMC2M). Made famous by one of Jacques Yves Cousteau's films (for our biopic see http://on.fb.me/1wcAeKd), it is a famous site in the diving world that he first made possible by inventing the aqualung.

The cave has already been used in research on Saharan dust transport across the Atlantic since its depths make an ideal sediment trap, and now new work has confirmed the inference from other sources that the Maya civilisation fell after a series of long droughts. They used a series of sediment samples from the epoch of their demise (around 800-1000 CE) and compared the changing ratios of aluminium and titanium, which reveal periods of heavy rainfall from tropical cyclones (the source of most of the water that kept the Mayans alive).

These indicated several long periods of drought at the time of their slow downfall that eked out over two centuries as the inter tropical convergence zone shifted north and south, taking the rain giving cyclones with it. The science is simple, in times of greater rain, more of the volcanic rocks in the area are weathered, and the water flows into the sea dumping its sediment and accompanying titanium with it. Analysing through the core allows the shifting rainfall densities to be tracked over time.

The new evidence joins other proxy data from stalagmites in caves, but the blue hole lies on the line of typical cyclone tracks and the Mayan capital of Tikal, sited in present day Guatemala, rendering its data more relevant. Despite their excellent water engineering in a resource poor karstic area (in which most of the water lies underground), the evidence (as outlined for example by Jared Diamond in his book Collapse: how societies choose to fail or survive) shows that a burst in population growth coincided with a long term decrease in rainfall, with several decades long droughts straining the culture beyond its capacities.

The civilisational collapse involved a population crash, the abandonment of the cities and a return to small scale subsistence agriculture, the entire culture nearly vanished from the record until its cities started to emerge from the jungles of Central America. The culture survived another century or so at Chichen Itza on the Yukatan peninsula, but the research shows that a second prolonged drought coincided with its abandonment.

The work also emphasises the link between ecology and climate. Some areas can take greater levels of strain and still keep going. The changes in European agriculture from the late medieval warm period, through the little ice age and intothe current warming reveals a certain integrity. The evidence revealing the Mayan demise implies that the area they lived in is much more sensitive to changing precipitation than some other areas of Earth.

The warning is clear, as the climate warms and rainfall patterns redistribute chaotically across the globe, some areas will take the strain better than others, but detailed ecological studies will be needed to quantify this (as much as we can) in order to help the most people survive the rough ride to the future (as James Lovelock's latest book puts it so well) that is already starting.

Loz

Image credit: USGS http://www.livescience.com/49255-drought-caused-maya-collapse.html http://www.theguardian.com/world/2015/jan/03/great-blue-hole-belize-clues-fall-mayan-civilisation http://io9.com/5886796/did-mild-weather-really-destroy-the-mayan-empire http://www.nature.com/srep/2014/140127/srep03876/full/srep03876.html#/results Papers, paywall access

http://www.sciencemag.org/content/338/6108/788 www.sciencemag.org/content/335/6071/956.abstract

Great Blue Hole, Belize

Overflight of the Great Blue Hole, Belize

West Indian Manatee, Belize

Close up stingray almost seems to be hovering over grass, Belize

The Great Blue Hole of Belize

One of the world's premier diving sites situated 96 Km offshore at Lighthouse Reef Atoll, it was first explored by Jacques Yves Cousteau aboard the Calypso using his famous one man submarine. Measuring 300 metres across by 125 deep, the colour is due to the depth of the water within. Blue holes are flooded karst cave systems that were filled as sea levels rose during the end of the last ice age. The hole leads to a series of passages and submarine caves, some still filled with stalactites from their aerial phase.

The bottom waters are anoxic, ensuring good preservation. The sediments have been cored in order to understand the journey of African dust from the Sahara to South America, where it provides nutrients to the Amazon rainforest (satellites have shown the greening of the jungle after deposition of dust).

A world heritage site since 1997, it is one of the country's national monuments as part of the Belize Barrier Reef Reserve System.

Loz

Image credit: Belize Tourism/Catlin Seaview Survey

http://ambergriscaye.com/pages/town/greatbluehole.html

http://www.youtube.com/watch?v=WMQgEhB2E5k http://soundwaves.usgs.gov/2001/06/ http://andrewbales.wordpress.com/2011/08/16/blue-holes/

Blue Hole from space

The Great Blue Hole off the coast of Belize (see http://on.fb.me/1KbMC2M and http://on.fb.me/1zgRUCj ) is one of the most iconic marine wonders and premier dive sites on Earth. Spectacular from the air, it's equally stunning from space, visible as the dark circle about 3/4 of the way up the photo, just right of centre.

Loz

Image credit: ALOS

Belize Barrier Reef

This photo shows the line of Belize’s Barrier Reef, an ecosystem of corals, mangrove swamps, and islands in the Caribbean. Charles Darwin described this reef “as the most remarkable reef in the West Indies” after visiting on his travels.

The reef is the longest barrier reef (tracking a shoreline) in the Northern or Western hemispheres. It is home to a number of endangered species, including turtles, manatees, and crocodiles.

It also hosts a variety of spectacular landscapes sculpted by sea level changes over the past several million years. For example, the spectacular Blue Hole (http://tmblr.co/Zyv2Js1ZtCSfP) is a karst feature, created when sea level dropped and parts of the limestone structure of the coral reef were exposed to rainfall and tropical erosion.

The Barrier Reef is considered a UNESCO World Heritage site, but it is also considered a threatened site. The fully protected Reserve area includes only 12% of the reef; the remainder is governed under a variety of laws and statuses. Fishing, tourism, and development have taken their toll on some sections of the reef, and the reef is also under stress from changes in ocean chemistry and warming waters like those in the rest of the world.

-JBB

Image credit: Ian Morton https://flic.kr/p/aEPM23

References: http://whc.unesco.org/en/list/764 http://bit.ly/21jus6T

Great Blue Hole sheds light on Maya collapse Located off the coast of Belize in an idyllic coral reef, the blue hole is part of a karst limestone landscape that was flooded by sea level rise at the end of the last ice age (see http://on.fb.me/1KbMC2M). Made famous by one of Jacques Yves Cousteau's films (for our biopic see http://on.fb.me/1wcAeKd), it is a famous site in the diving world that he first made possible by inventing the aqualung. The cave has already been used in research on Saharan dust transport across the Atlantic since its depths make an ideal sediment trap, and now new work has confirmed the inference from other sources that the Maya civilisation fell after a series of long droughts. They used a series of sediment samples from the epoch of their demise (around 800-1000 CE) and compared the changing ratios of aluminium and titanium, which reveal periods of heavy rainfall from tropical cyclones (the source of most of the water that kept the Mayans alive).  These indicated several long periods of drought at the time of their slow downfall that eked out over two centuries as the inter tropical convergence zone shifted north and south, taking the rain giving cyclones with it. The science is simple, in times of greater rain, more of the volcanic rocks in the area are weathered, and the water flows into the sea dumping its sediment and accompanying titanium with it. Analysing through the core allows the shifting rainfall densities to be tracked over time.  The new evidence joins other proxy data from stalagmites in caves, but the blue hole lies on the line of typical cyclone tracks and the Mayan capital of Tikal, sited in present day Guatemala, rendering its data more relevant. Despite their excellent water engineering in a resource poor karstic area (in which most of the water lies underground), the evidence (as outlined for example by Jared Diamond in his book Collapse: how societies choose to fail or survive) shows that a burst in population growth coincided with a long term decrease in rainfall, with several decades long droughts straining the culture beyond its capacities. The civilisational collapse involved a population crash, the abandonment of the cities and a return to small scale subsistence agriculture, the entire culture nearly vanished from the record until its cities started to emerge from the jungles of Central America. The culture survived another century or so at Chichen Itza on the Yukatan peninsula, but the research shows that a second prolonged drought coincided with its abandonment.  The work also emphasises the link between ecology and climate. Some areas can take greater levels of strain and still keep going. The changes in European agriculture from the late medieval warm period, through the little ice age and intothe current warming reveals a certain integrity. The evidence revealing the Mayan demise implies that the area they lived in is much more sensitive to changing precipitation than some other areas of Earth. The warning is clear, as the climate warms and rainfall patterns redistribute chaotically across the globe, some areas will take the strain better than others, but detailed ecological studies will be needed to quantify this (as much as we can) in order to help the most people survive the rough ride to the future (as James Lovelock's latest book puts it so well) that is already starting.  Loz Image credit: USGS http://www.livescience.com/49255-drought-caused-maya-collapse.html http://www.theguardian.com/world/2015/jan/03/great-blue-hole-belize-clues-fall-mayan-civilisation http://io9.com/5886796/did-mild-weather-really-destroy-the-mayan-empire http://www.nature.com/srep/2014/140127/srep03876/full/srep03876.html#/results Papers, paywall access http://www.sciencemag.org/content/338/6108/788 www.sciencemag.org/content/335/6071/956.abstract

The Great Blue Hole off the coast of Belize - it's exactly what it sounds like. -E