The Earth Story

Cairo and the Nile by night and day

4000 years have passed since the advent of the Pharaoh, but the River Nile still remains the pulse of Egyptian metropolitan activity. Both images, captured by astronauts from the International Space Station, show the intricacies and breadth of the Nile Delta, as well as the city of Cairo at the delta’s apex. During the day, the Nile Delta appears as a floodplain with prosperous vegetation, in stark contrast to the barren sands of the surrounding desert. At night, the urban network of Cairo shines like the brightest bulb in a chandelier — the metropolis is the largest city in the Middle East and constitutes one-fifth of Egypt’s population. Less luminous are the towns and villages along the Nile Valley and the Nile Delta, but the lights are still bright enough that you can trace the dark lines of the River Nile and the many branches of the Nile Delta that flow into the Mediterranean Sea.

-DC

Photo credits: https://archive.org/details/PIA02647 https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=ISS025&roll=E&frame=9858

Original caption:

Original caption:

Dusk til dawn over the Middle East, including Dubai, Sharjah, and Syria - before the war started.

Original caption:

Liwa Desert

Evidence of Middle Eastern megadroughts comes to light

A core drilled under the slowly drying Dead Sea (see http://bit.ly/2oeU6hH) contained salt layers between the more normal lake bottom mud, the thickest being 100 metres. These record past periods of dryness beyond any experienced in recorded history, some 120,000 and 10,000 years ago. Sitting some 300 metres below the surface the layers record extended periods when the rainfall was 20% of modern levels, a situation that would prove catastrophic in the modern world.

The causes back then were minor oscillations in the world system as atmospheric flows shifted, but scientists were surprised by their magnitude, since current models did not tease such events out of the data. In other words the region got drier in reality than was thought was possible in theory.

The first event records a drying out of the closed basin (fed by the Jordan drainage basin) during the last great interglacial period, at a time when temperatures were some 4 degrees Celsius hotter than last century's average, a scenario within the bounds of possibility for the coming century recorded by the IPCC. The team analysed layer by layer the changing chemistry of fluid inclusions within the salt crystals to deduce past rainfall and runoff patterns, revealing a 50-80 percent decline lasting for decades or centuries each time.

As the region is already suffering the worst drought in a millennium (average rainfall has fallen 10% since 1950, models predict a potential 20% more this century) and the world continues to warm from our modern atmospheric stimulation, the likelihood increases of such events returning in the future. Since the current dry period was recognised as a contributing factor in both the Arab Spring and the ongoing horrors/knock on effects of the Syrian civil war (see http://bit.ly/2o6rwPF), the possibly is preoccupying in an area already rent with tensions, tight water supplies (some 10% per capita of the world average), a fast growing frustrated and impoverished population and many layers of ongoing conflict.

The same climatological risks have been recognised in the western USA (see http://bit.ly/2nQZRib and http://bit.ly/2ommHlK), itself just recovering from a multi year drought.

Loz

Image credit: The Dead Sea; Vladimir Popov Uhaiun

http://bit.ly/2nShbog http://bit.ly/2mQ2KnM

Color Changing Lake

These two satellite photos show Lake Urmai, a saline lake in Iran, as seen in April and July of this year. Fair to say something has changed between the two shots.

Lake Urmia used to be the largest saltwater lake in the Mideast, but water diversions in recent years have cut the flow of water into the lake and reduced its size (https://tmblr.co/Zyv2Js1bzMEJU). As less water flows in, the lake gets saltier, and as it gets saltier only certain organisms are able to thrive.

In the second photograph, taken in July, the lake is bright red. The saline water has prevented growth of anything that would outcompete a certain organism, most likely a type of algae called Dunaliella salina. In saline environments, that algae produces caretoids to protect its cells and those chemicals can dye the surrounding waters bright red. Other organisms may contribute as well.

The lake has shifted back and forth from green to red several times in recent years, and reddenings like this are likely to become more common as it approaches complete drying.

-JBB

Image credit: NASA/USGS/Landsat http://go.nasa.gov/2aeZfNy

Ararat

This gorgeous cone is one of several volcanoes in Eastern Turkey; it is considered a religious or holy site by several religions and is a national symbol of Armenia, just across the border.

The taller of two Ararat peaks is treeless, with an elevation of 5137 meters. It is volcanic, forming in a tectonic basin created as the Anatolian plate is pushed to the East, creating strike slip faults with large steps in-between. A basin in-between faults, where the crust is pulled apart, can allow hotter mantle material to rise up and begin melting.

Volcanism has occurred in this area for over 10 million years. The peak of volcanism occurred about 5 million years ago, after which point the volcanism moved to specific vents such as Ararat. Like many volcanoes, it grew in several pulses, including both explosive eruptions and lava flows.

Ararat’s last known eruption was in 1840 and further eruptions are likely at some point in the future (the volcano shows no signs of activity today, but it likely still has an active magma system at depth beneath it).

-JBB

Image credit: Alexander Mkhitaryan https://flic.kr/p/eg8sa8

References: http://go.nasa.gov/1n9u5NM http://bit.ly/1P6SEan http://www.sciencedirect.com/science/article/pii/S0377027398000559 https://www.uwgb.edu/dutchs/Turkey71/Geology.HTM http://volcano.si.edu/volcano.cfm?vn=213040 http://bit.ly/1Q5U0iw