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Coral reefs - Rás Muhammad EarthCache

Hidden : 01/17/2010
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Geocache Description:

The growing of coral reefs is nowadays the most visible "geological" formation. The deformation of rocks has been done, except of vulcanic activity the reefs are the only active power which change the surface of our planet. And also the man helps with the creation. He sank the old boats to the bottom of the sea to provide the corals the possibility to create new coral atoll. The Red Sea is known as the most beautiful coral region. And what are these amazing employees of the Earth?


Coral Reefs

Coral reefs can be made up of hundreds of different species of coral. There are two main types: "hard" coral with an outer skeleton of calcium carbonate (CaCO3) and "soft" corals that embed bits of CaCO3 inside their bodies. Although it comes in many shapes and sizes, all coral is composed of tiny individual polyps. A polyp is a tiny animal that looks like an upside-down jellyfish.

In soft corals, each polyp contains little spikes of CaCO3 that help hold many polyps together in structures that look like fans or whips. In hard corals, polyps sit inside little cups which they build out of calcium carbonate. Many of these cups are cemented together to make up a coral colony. Reefs are formed when hundreds of hard coral colonies grow next to and on top of each other. Since most species of coral polyps stay deep within their calcium carbonate cups during the day, the casual observer may think of coral as inanimate rocks. At night, however, the polyps emerge, and wave their tiny stinging tentacles in the water to catch microscopic organisms called plankton.

What makes coral polyps so unique is that plankton is only part of their diet. Each polyp harbors within its body special algae called zooxanthellae. These one-celled plants use sunlight and carbon dioxide to conduct photosynthesis, a process that produces oxygen ... and other nutrients needed by the polyps. In return, the algae get protection and a constant supply of carbon dioxide and other raw materials they need for photosynthesis. Such a mutually beneficial relationship is called symbiosis. Without this special relationship, it is likely that there would be far fewer animals in clear, tropical waters since they typically cannot support life. It is important to realise that the fish, crabs, snails, worms and other reef creatures depend on the health and growth of the coral reef for their existence.


Types of reefs

Coral reefs are divided into four main types: fringing reef, platform reefs, barrier reefs and atolls.

Fringing reefs are relatively young. They can develop in shallow waters along the coast of tropical islands or continents. The corals grow upwards to sea level or just below and outwards towards the open ocean. Fringing reefs are generally narrow platforms a short distance from shore and don't contain a substantial lagoon.

Platform reefs usually lie in sheltered seas and quite far offshore. They are flat-topped with small and very shallow lagoons.

Barrier reef - A coral reef growing parallel to the coastline and separated from it by a lagoon is called a barrier reef. The lagoon may develop between the fringing reef and the land. As the reef continues to grow further and further offshore it eventually reaches the edge of the continental shelf. Barrier reefs can also originate offshore if the depth of the seabed out there is shallow enough to allow corals to grow.

Atolls are rings of reef, often encircling an island (sand and coral rubble). They typically have a shallow, sandy, sheltered lagoon in the middle. Access to the open sea beyond is through a number of channels. These provide fresh and colder water for the lagoons. Corals atolls are on the top of submarine mountains. These mountains are remnants of volcanos. Once there were fringing reefs around the volcano. As it slowly submerged the corals continued to grow up to the surface of the water. What remained after the volcano became invisible is a ring of coral reefs surrounded by deep ocean.

Fringing reef Platform reef Barrier reef Atoll

However some atolls were probably formed by rising sea levels rather by the sinking of islands. Other theories suggest that corals colonized eroded limestone formations, so called karstic saucers.

a fringing reef surrounding an active volcano - subsidence of the seafloor or rising sea levels

shrinking of the island - an atoll results when the island has disappeared


Reef morphology


Reefs are often referred to as the "rainforests of the oceans". Coral reefs host an extraordinary variety of marine plants and animals (perhaps up to 2 million) including one quarter of all marine fish species. The wide variety of habitats depends a lot on the morphology of the coral reef. The differences in temperatures, light, exposure to waves and tides, currents and the amount of food available result in different habitats and niches.

A) Mud flats close to shore with tide pools - B) Mangroves - C) Seagrass bed - D) Patch reefs on inner reef slope - E) Inner lagoon - F) bottom with mud - G) Pinnacle - H) Outer lagoon - I) Fine sand - K) Acropora corals - L) Algae ridge - M) Sand and rubble - N) Gorgonians and black corals - O) Cave or overhang

Rás Muhammad (Ras Mohamed / Ras Mohammed)


Ras Muhammad is a national park in Egypt at the southern extreme of the Sinai Peninsula, overlooking the Gulf of Suez on the west and the Gulf of Aqaba to the east. The park is situated in the tourist region of the Red Sea Riviera, located 12 km from the city of Sharm-el-Sheikh. The park spans an area of 480 km⊃2;, including 135 km⊃2; of surface land area and 345 km⊃2; area over water. Marsa Bareika is a small bay inlet in Ras Mohammed, and Marsa Ghozlani is a very small inlet located across from the park visitors center.

Coral reef ecosystems found in the National Park are recognized internationally as among the world's best. This recognition is based primarily on the diversity of flora and fauna, clear warm water devoid of pollutants, their proximity to shorelines and their spectacular vertical profile. The reef exists as an explosion of color and life in stark contrast to the seemingly barren desert adjacent to it. In reality, the desert is rich in fauna, mainly nocturnal. These ecosystems are intrinsically linked and thus must be managed as a single unit. The National Park offers outstanding coral reef and nature viewing experiences to the visitor. The Eel Garden, named for its population of garden eels at 20m, also provides excellent and calm conditions. The Main Beach, often crowded, remains one of the best locations to see vertical coral walls. Access is restricted to the left side of the bay. The Old Quay, often calm but having more turbid water, has some of the best shallow water reef structure.




Your tasks


  • In Ras Muhammed (on surface area) you can find great crack formations in the earth. Is there fresh or salt water?
  • How many species of corals were found in Ras Muhammad?
  • Put photo of you with GPS on the site to the log.

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