The Earth Story

Why are oceans salty? Oceans have saltwater but rivers and most lakes do not. Why? Where did the salt come from?

Salt Casts These are tiny cubes of mud found in one of the rocks of the Belt sequence of modern-day Montana. These Precambrian aged rocks were deposited over a billion years ago as a rift opened along the coast of the continent Laurentia, which would eventually go on to make up the bulk of North America. That rifting created deep basins where sediments could accumulate, giving us the modern day Belt rocks.

@dji_ars @djiglobal

Pink lake in Turkey

The "Dying" Sea?

The Dead Sea is a hypersaline lake with a salinity level of 33.7% that borders Jordan, Israel and the West Bank and covers an area of ~600 km2 (230 sq mi). Hypersaline means that it has an unusually high concentration of salts (sodium chloride and others) and has a higher salinity than the ocean (3.5% salinity). While the Dead Sea is not the saltiest lake in the world - that honour belongs to the Don Juan Pond in Antarctica - it is the deepest, with a maximum depth of 307 m (997 ft) below the surface. The lake is also Earth's lowest point on land with the lake's surface at an elevation of 429 m (1,407 ft) below sea level.

The name “Dead Sea” refers to the fact that most life forms (with the exception of some bacteria and microscopic algae) cannot survive in its waters. However, the lake has drawn interest from medical researchers who are using the unique chemical and physical properties of its mud and water to treat number of health conditions including psoriasis (a chronic skin condition) and osteoarthritis of the knees.

Sadly, the Dead Sea may be dying. Due to water diversion from the Jordan River which normally flows in from the north (visible as a thin line at the top of the image), the level of the lake (as well as the undelying groundwater) has dropped significantly. The image I've included shows the drop in water level since 1972. At the southern end of the lake you can see the mineral evaporation ponds from which carnalite (potassium magnesium chloride) is harvested.

As a result, sinkholes (up to 1 per day) have begun forming in the area as briny groundwater is flushed out by freshwater. The freshwater then dissolves away the rock, forming caves. that grow larger and collapse, causing sinkholes and an elaborate underground drainage system. This link (https://bit.ly/2JpuXgh) describes the causes and consequences of the Dead Sea decline.

Past articles: Extreme environments - http://on.fb.me/1vEdUEm

Image credit: NASA image by Robert Simmon, using Landsat data from the United States Geological Survey. Caption by Aries Keck and Mike Carlowicz. (http://visibleearth.nasa.gov/view.php?id=77592). I recommend checking out this link as it describes the colouration of the image and a bit about the cultural significance of the Dead Sea. Further reading: More on the Dead Sea - The chemistry and biology of the Dead Sea -http://bit.ly/1D4DevS More on the Lisan karst system - http://bit.ly/1Bqjzmk(requires login via your local library)

Teepee Structure

Lake Amadeus

Around 50 kilometres from Uluru (also known as Ayers Rock) in Australia's red dusty centre, are a couple of large salt lakes, waxing and waning in size and depth with the cycles of drought and rain. The larger of the two is Lake Amadeus (180x10km), located in a geological basin of the same name filled with sediments from a nearby mountain building event during the Ediacaran era, shortly before the Cambrian kicked off.

The lake is often mostly empty, filled with a brilliant white crust of salt, but on after the rare occurrences of heavy rainfall it becomes part of a flowing drainage system made of similar evanescent water bodies that drains into the Finke river. Amadeus is also partly fed by springs, a vital source of water for the indigenous owners of the land, who have relied on them since time immemorial.

Loz

Image credit: Bernhart Edmaier

http://www.lrm.nt.gov.au/__data/assets/pdf_file/0004/13882/59_lakeamadeus.pdf

Bi colored lake Astronaut Randy Bresnik captured this view of Utah’s Great Salt Lake out the windows of the International Space Station. A causeway that carries rail traffic across the lake also limits flow of lake water from north to south. The northern part of the lake is saltier, preventing many organisms from living there except for microscopic algae, which have pigments that dye the lake colors. To the side of the lake you also see some reddish colored evaporation ponds, where lake waters are being evaporated so that salt can be harvested. They are colored by the same salt-tolerant organisms. -JBB Image credit: Randy Bresnik https://twitter.com/AstroKomrade/status/937709538278481920

Backpacker floating in a salt-encrusted pond surrounded by the rest of the Atacama Desert (I hope this is legal!).

If you have been online over the past few years, you have probably come across this image along with some kind of explanation that the animals have turned to stone and died- this is a bit misleading.

The area in question here is Lake Natron in Tanzania. The waters of this lake are alkaline, with a pH as high as 10.5; caustic enough to burn skin. Lake Natron's unusually harsh composition comes from a unique neighboring volcano, Ol Doinyo, which discharges alkali-rich natrocarbonatites that end up in Lake Natron via rainwater runoff.

Despite the basic nature of the lake, life has not only adapted to this harsh ecosystem but it actually thrives. The environment here supports many species, but is a breeding ground for flamingos and other wetland birds.

In fact, more than 2 million lesser flamingos (Phoenicopterus minor) utilise the lake as their primary breeding ground. The flamingos' nests are built on small islands that form in the lake during the dry season.

Nick Brandt, the photographer, visited the lake and founds the remains of flamingos and other animals which he then posed them as they would be if alive. As depicted in the photo, the animals were covered in a chalky sodium carbonate or bicarbonate deposit- but Thure Cerling, professor of geology and geophysics at the University of Utah, suggests that this is not what killed the animals and they most likely died of natural causes. Since there are few predators in the area, their bodies remain and become salt-encrusted when the lake's water level drops.

Lake Natron is one of two alkaline lakes in that area of East Africa; the other is Lake Bahi. Both are terminal lakes that do not drain out to any river or sea but instead are recharged by small rivers and hot springs.

-Jean

To see more images, go here: http://bit.ly/1buYIFQ_ _

Salt from the Sea The shoreline of the Dead Sea is ringed with white layers of salt, deposited out of the hypersaline water. The salinity gives the Dead Sea its name - no life besides bacteria can endure it - and is a result of its nature as an "endorheic" lake. The Dead Sea and the surrounding watershed form a closed drainage basin within the Jordan Rift Valley; water flows in from the River Jordan and Wadi Mujib, but has no way to escape besides evaporation and seepage, a situation that is referred to as endorheic. High evaporation rates in the hot, dry climate lead to the concentration of minerals in the water, creating highly saline conditions and ribbons of white deposits tracing its shores. -CEL Source: http://bit.ly/2oiJ1Jj Image: http://bit.ly/2pnSCR1 Credit: Djamil Al-Halbouni (distributed via imaggeo.egu.eu)