Posted on July 23 2019
Maybe you remember the old riddle from your childhood: What happens if you drop a white hat in the Red Sea? Aside from the answer, which never fails to get a disappointed groan out of kids, what is there to know about the Red Sea? Where is it, and how did it get there? The Saudi Peninsula, home to Saudi Arabia, as well as Yemen, Oman, Kuwait, the United Arab Emirates, and tiny Qatar and Bahrain, pokes out of southwest Asia into the Arabian Sea like a big, thick ski boot. On its east side is the Persian Gulf and the Gulf of Oman. Its wide southern terminus is defined by the Arabian Sea and the Gulf of Aden, an arm of that sea. Its long western edge is shaped by today’s subject, the Red Sea. The sea is nothing if not linear as it runs the length of the Saudi Peninsula, separating that landmass from the African continent. At roughly 1,200 miles in length, but generally only 100 miles or so in width, the Red Sea is indeed a long, thin body. Just 190 miles at its broadest point, it pinches down to a mere dozen miles in width at its southern end. This spot is the Bab el-Mandeb, a narrow strait between Yemen, on the peninsula, and Eritrea and Djibouti on the African side. The sea’s northern end is sort of plugged by the “cork” of the Sinai Peninsula, which itself is defined by two small extensions of the Red Sea, the Gulf of Aqaba and the Gulf of Suez. The plug has leaked, so to speak, since 1869, when the Suez Canal was opened, creating a navigable waterway north to the Mediterranean. The Red Sea’s western shores include Sudan and Egypt, and Israel and Jordan dip their toes into the Gulf of Aqaba, so along with the other defining nations, there is no shortage of tension in the Red Sea region. Unfortunately, the political and cultural animosities there have slowed or denied a lot of valuable academic study.
Long before that part of the world developed so many disputes between the local populations, perhaps as early as 55 million years ago, the African and Arabian tectonic plates parted ways and created a rift valley that has been filled with the waters of the Red Sea. Similar divergences created the East African Rift System to the south, the rifts that form the Dead Sea to the north, and an eastward branch that filled with the Gulf of Aden. A trough that goes as deep as 4,000 feet runs down the middle of much of the Red Sea’s narrow basin. However, at its southern end the depths are much shallower, and coral reefs further constrict passage, leaving only 380 feet in depth. The southern end also has a number of islands, which are remnants of reefs formed when the sea was deeper. Some other islands are volcanic, which is no surprise, given the tectonic activity in the area. The thinning of surface rock along the rift also allows for hydrothermal vents deep in the Red Sea, where metal-rich sediments are found to be several tens of feet thick. While the crustal movements that formed these areas began long ago, evidence suggests those processes have become more active in the last 10,000 years, and continue today.
The desert lands that surround the Red Sea offer up no rivers to add to its volume, and the relentless sun peels away more than 80 inches of its surface volume annually. Through that tight constriction at the Bab el-Mandeb, outside seawater flows in to replenish that which is lost to the heat. Southerly winds push that water north toward the shallow Gulf of Suez, where intense evaporation raises salinity and density even higher. These dense northernmost waters then sink and flow southward, eventually exiting at the Bab el-Mandeb beneath the incoming waters. Through this conveyer belt movement, the process of changing out the whole of the Red Sea’s waters is calculated to take about 20 years. It is plenty warm enough to enjoy a comfortable swim anywhere in the Red Sea, as warm as 86 degrees Fahrenheit, but at a certain depth the water cools to around 72 degrees F. In the great depths of the central trough, however, a hypersaline brine pool of 140-degree water heated by the hydrothermal vents makes for some truly scalding conditions. There’s no oxygen down there either, so even if you were a heat-tolerant fish, you would find it unlivable. The same winds that drive the circulating currents north can also blow huge swarms of locusts—the likes of which are recounted in biblical passages—with the coming of the monsoon season. As in days of yore, these billions of insect mouths still lay waste to all the plant life they encounter, wiping out farmers’ crops. Even a small invasion of these hungry swarms can eat the food of 35,000 people a day, severely impacting the economy and well-being of the Red Sea populace.
Things like locust plagues take a toll on the less-industrialized region. Unlike the wealthier Persian Gulf, the Red Sea area is not known for its oil deposits because the depth and rough floor of the Red Sea make exploratory drilling difficult. Some petroleum extraction does take place there, though, as well as mining for evaporite minerals left behind by historically drying seas. There is also the potential for mining the seafloor for the valuable metals in the ooze down there, but so far it has not been pursued. The main value of the Red Sea is its position between the Mediterranean and the Arabian Sea. The completion of the Suez Canal made the Red Sea a valuable conduit for commerce and an essential highway for military movement. But sailing those waters is not without hazards even beyond those posed by humans. Winds that bring sandstorms, unusual currents, and distorted optics caused by heat can plague mariners. Heading for the safety of a natural port is not much of an option along the relatively smooth coastline. Coral, a diminishing commodity in much of the world, creates more headaches for sailors as its growth narrows the passage at the Bab el-Mandab and has to be blasted away to keep access open.
Boats have been plying the waters of the Red Sea since ancient times despite the challenges, and Moses is said to have called upon higher powers to part its waters entirely, in order for him and his fellow Israelites to escape the attacking Egyptians. As a side note of interest, a geographer with some biblical background has posited that that event may have occurred farther north, in a part of the Nile Delta. The scholarly debate over the exact location of the sea’s parting has led some to conclude that “Red Sea” was a misnomer applied to “Sea of Reeds,” in a phrase translated from the Hebrew. “Sea of Reeds,” on the other hand, is an apt description of parts of the Nile Delta. Powerful easterly winds, which sometimes occur there, may have pushed the shallow waters of an estuary back into a lake basin for a few hours, allowing Moses and his people to make the crossing of an otherwise water-covered land bridge. It’s one of those “well, it could have happened” sort of ideas, and has gotten mixed reviews from both the scientific community and the faithful.
However one sees the story of Moses, another great mystery may still be on your mind: Why is it called the Red Sea, anyway? No, it wasn’t named by communists. Trichodesmium erythraeum, a form of algae that inhabits those waters, occasionally blooms and then forms a “red tide” as these phytoplankton die off. Hence, the name. Still, it’s not like a sea of red paint, and the waters are more commonly crystal clear. So what does happen when you drop a white hat in the Red Sea?….it gets wet. Hey, c’mon, it is a kid’s joke, after all. Here’s hoping that reading this far provided you, besides the groan, a little more knowledge of the Red Sea region, a fascinating place that really deserves more attention than it gets.
The pyramids aren’t the only thing to see when you take a trip to Egypt—head on over to the beaches and scenery of the Red Sea! This wall map of the country will guide you there. And you can get it from Maps.com.
caption: Saudi Arabia has the most Red Sea coastline, although Egypt is close if you count its contact with the Gulf of Suez and the Gulf of Aqaba around the Sinai Peninsula, at the top end of the sea.
source: Wikimedia Commons: CIA Factbook (Public domain)
caption: Detail of the Sinai Peninsula, bounded by the Gulf of Suez and the Gulf of Aqaba, arms of the Red Sea.
source: Wikimedia Commons: CIA (Public domain)
caption: The separation of the African and Arabian plates created the basin for the Red Sea.
source: Wikimedia Commons: Richard M. Pollastro, USGS (Public domain)
caption: The bathymetry on this map shows the deep central trench at the bottom of the Red Sea.
source: Wikimedia Commons: Eric Gaba (Sting – fr:Sting) (CC by SA 4.0 International)
caption: Steep, dry mountains like these along the Gulf of Aqaba parallel much of the rest of the Red Sea.
source: Wikimedia Commons: Romazur (CC by SA 3.0 Unported)
caption: Red Sea coral is prolific, and seems to be more resilient in the face of warming waters that are plaguing corals in other parts of the world.
source: Wikimedia Commons: Hagainativ (CC by SA 3.0 Unported)