Why the Red Sea is Called the Red Sea?

The world is covered by vast, incredible oceans and seas. These massive bodies of saltwater are crucial to life, influencing our weather, providing food, and serving as vital pathways for global trade. Think of the seven seas, a historical term referring to different parts of the ocean. While the definition has changed over time, it highlights the importance of these waters. Some seas have purely descriptive names, like the Caribbean Sea. Others have nicknames; the Mediterranean Sea, for instance, is sometimes called the "Great Sea" or "Our Sea". But what about the Red Sea? Its name stands out. Why isn't it called the Blue Sea or the Green Sea? Have you ever wondered why this famous body of water between Africa and Asia is known as the Red Sea? Do you know the theories behind its intriguing title? In this article, we'll take a look at the different explanations for how the Red Sea got its name.

Where is the Red Sea?

The Red Sea is a vital, narrow inlet of the Indian Ocean, strategically located between Africa and the Arabian Peninsula (Asia). It stretches over 2,250 km, bordered by six countries: Egypt, Sudan, Eritrea, and Djibouti on the west and Saudi Arabia and Yemen on the east, plus Israel and Jordan on the Gulf of Aqaba. Geologically, it's a young, widening rift valley within the Great Rift Valley, formed as the African and Arabian tectonic plates slowly pull apart. This makes it a deep body of water (with a maximum depth of over 3,000m).

It's also one of the world's hottest and saltiest seas due to high evaporation and a lack of river inflow. Its name, a translation of the Greek Erythra Thalassa, most likely comes from seasonal blooms of reddish algae (Trichodesmium erythraeum). It connects to the Mediterranean Sea via the Suez Canal, making it a crucial global trade route.

10+ Lesser-Known Facts About the Red Sea

• About 10-20% of its marine species (fish, coral) are found nowhere else on Earth.
• Its southern connection to the Indian Ocean is the Bab-el-Mandeb Strait, whose name means "Gate of Tears" in Arabic.
• Deep in the rift valley, there are brine pools and hot metal-rich muds caused by hydrothermal activity.
• Due to its high salinity (saltiness), swimming in the Red Sea is surprisingly buoyant.
• The Red Sea is famous for its concentration of well-preserved shipwrecks, making it a top diving destination.
• It was a key part of the ancient Spice Route and was explored by the Egyptians as early as 2500 BC.
• The central part of the Red Sea experiences a minimal tidal range.
• The Red Sea is a geologically young rift valley, slowly widening as the African and Arabian tectonic plates pull apart. It's essentially an ocean in the early stages of formation.
• It is one of the world's saltiest seas, with salinity levels up to 41 parts per thousand (ppt) in the north (the global average is about 35 ppt). This is due to high evaporation and a lack of river inflow.
• Corals in the northern Red Sea's Gulf of Aqaba are exceptionally resilient to high temperatures. Scientists believe they adapted to thermal stress while migrating through the warmer southern waters, offering a unique "refuge" against global warming.
• At depths over 2,000 metres in the central trough, there are areas with hot, hypersaline (extremely salty) water pools. These anoxic (oxygen-free) pools can reach temperatures up to 60°C (140°F).
• The sediments beneath the hot brine pools are rich in heavy metal oxides (such as copper, zinc, and silver) deposited by hydrothermal vents, making them a potential deep-sea mineral resource.
• Roughly 10–20% of its marine species, including fish and corals, are endemic, meaning they are found nowhere else on Earth. This isolation stems from geological history and high salinity.
• The central region near Jeddah has a minimal tidal range (often less than $0.3$ meters). The annual changes in water level caused by seasonal weather are actually more significant than the daily tides.
• Despite being far north of the equator and surrounded by desert, it enjoys consistent warmth, which supports extensive, thriving tropical coral reef systems.
• The water has exceptional clarity, a non-obvious scientific fact. This is because no major rivers or permanent streams flow into it, minimising the sediment and particulate matter that typically clouds coastal waters.
• Water exchange with the Indian Ocean is constricted by the narrow Bab-el-Mandeb Strait (Gate of Tears). This constriction, combined with seasonal monsoons, creates unique, reversing surface currents in summer and winter.
• The Red Sea Rift is still volcanically active. New landmasses have emerged in the southern part, such as those in the Zubair Archipelago, due to ongoing tectonic spreading and underwater eruptions.

Why is the Red Sea called the Red Sea?

The Red Sea's name originates from several potential sources, with the most prominent theories related to seasonal blooms of reddish algae and ancient use of colours to denote cardinal directions. The water itself is typically a clear blue-green. 

Key Theories on the Origin of the Name

• Reddish Algae Blooms: The most popular hypothesis is that the name comes from a type of cyanobacteria (algae) called Trichodesmium erythraeum. When these vast blooms of algae die off, they turn the typically blue water reddish-brown near the surface, a colour ancient mariners may have observed.
• Cardinal Directions: In some ancient Asian languages, colours were used to represent cardinal directions. "Red" often referred to the south, just as "black" (Black Sea) referred to the north. From an Anatolian or Greek perspective, the sea was to the south, so the name might literally mean "Southern Sea".
• Red-Coloured Mountains/Land: Another theory suggests the name derives from the reddish, iron-oxide-rich mountains and rock formations that line parts of its coast, such as the western shore of the Arabian Peninsula.
• Ancient Translations: The name "Red Sea" is a direct translation of the ancient Greek name Erythra Thalassa. In Hebrew, it is called Yam Suph, which most likely translates to "Sea of Reeds", a reference to the abundant papyrus reeds in the Gulf of Suez area. The Greek translation of Yam Suph in the Septuagint rendered it as "Red Sea", which became widely used in European languages.

Why is it called the Red Sea if it's blue?

The most widely accepted scientific theory is that the name originates from periodic, large-scale blooms of the cyanobacterium (often called blue-green algae) Trichodesmium erythraeum.

• Reddish Hue: When these tiny, plant-like organisms die off, they turn a reddish-brown colour, forming extensive patches near the water's surface.
• Ancient Name: The English name is a direct translation of the ancient Greek name, Erythra Thalassa (Red Sea), suggesting early mariners observed this colouration phenomenon.
• Other Theories: Some scholars suggest the name is linked to a system in which colours represent the cardinal directions in specific Asian languages, with "red" signifying the South (the sea's location relative to ancient lands).