Vanished Reading Passage
Vanished Reading Passage
A.
Who blocked off the plug on the Mediterranean? And could it possibly happen again? By Douglas Mclnrris Cannes. Monte Carlo. St Tropez. Enchanting names all. And a significant contribution comes from the magnificent blue water that laps their coasts. But what if somebody cut off the plug? Assume The Mediterranean Ocean vanished, leaving a salt desert the size of India. Tough to consider? It happened.
B.
From the Lamont-Doherty Earth Observatory in New York, one of the team's leaders discovered the Mediterranean had once dried up, then replenished in a deluge of Biblical proportions. Bill Ryan says, ‘It would have resembled Death Valley.’ The Messinian Salinity Crisis - A wrenching series of extinctions and the onset of an ice age were caused by a global chemical imbalance between five and six million years ago due to the vast desiccation.
C.
When geologists discovered that major rivers flowing into the Mediterranean had eroded deep canyons in the rock at the bottom of the sea, The first indications of some exceptional previous events appeared in the 1960s. River erosion of bedrock cannot occur below sea level. However, the Rhone River in southern France carved a 1000-metre-deep tunnel into the seabed, while the Nile created a roughly 1,500-metre-deep channel into the bedrock off the coast of Africa. There was more: although caves can only be formed above water, scientists have uncovered a whole network beneath the island of Malta that reached an astounding depth of 2000 metres below sea level.
D.
In 1970, when an international team travelled the Mediterranean in a drilling ship to investigate the seabed near the Spanish island of Majorca, further evidence was revealed. Core samples started to reveal unusual occurrences: More than two kilometres beneath the current sea level, tiny plants and soil are trapped between salt beds. The plants grew under direct sunshine. Also found inside the rock were fossilised shellfish from shallow water and salt and silt: Particles of sand and mud that were originally transported by river water. Could the bottom have ever been close to the coast?
E.
This issue inspired Ryan and Kenneth Hsu, his co-team leader, to put together an astonishing sequence of occurrences. They found that the Mediterranean was progressively blocked off from the Atlantic Ocean around 5.8 million years ago, when continental drift wedged Morocco against Spain. As the gap narrowed and swallowed, the deep outward flow from the sea to the ocean was gradually cut off, leaving only the shallow inward flow of ocean water into the Mediterranean. When this water drained, the sea became progressively salty, and organisms that couldn't withstand the increasing salt concentration perished. Ryan says, ‘The sea’s interior was lifeless as a doornail, except for bacteria’. The Mediterranean dried up and died when the shallow entrance at Gibraltar ultimately closed entirely, enabling only rivers to nourish it.
F.
Meanwhile, the evaporated water returned to Earth as rain. As freshwater entered the oceans, it lowered their salinity. Parts of the ocean that would not ordinarily freeze started to do so since there was less salt to act as an antifreeze. Ryan states, ‘Sunlight is reflected into space by the ice’. ‘The planet cools. Do you bring about an ice age by yourself?
G.
Ultimately, a minor break in the Gibraltar dam interrupted the process. Seawater created a narrow path to the Mediterranean. As the chasm deepened, the water flowed faster and faster until the torrent tore across the newly formed Strait of Gibraltar at more than 100 knots. In his book The Mediterranean Was a Desert, Hsu said that Gibraltar Falls was 100 times larger than Victoria Falls and 1,000 times more magnificent than Niagara (Princeton University Press, 1983).
H.
In the end, the massive inland sea's swelling waves submerged the falls, and warm water started to escape to the Atlantic, warming the seas and the earth. Around 5.4 million years ago, the salinity problem ended. It lasted around 400,000 years. Subsequent drilling expeditions have complicated Ryan and Hsu's thesis. For instance, Scientists have found salt layers that are more than two kilometres deep – so thick, they argue, that the Mediterranean must have periodically dried up and refilled. Yet, they are only geological details. For visitors, the essential issue is whether or not it may occur again. Should Malaga start stockpiling dynamite?
I.
Not just yet, says Ryan. If continental drift does ultimately reseal the Mediterranean, it will require millions of years. Some future creatures may confront the problem of how to react to the extinction of nature. That is not anything about which our species must be worried.
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