Origin and geology About 40 million years ago, during the tertiary period, a series of tectonic movement disrupted the surface of the earth and led to the information of the Alps and the Himalayan mountains. In that period the African and Asian plates began to separate, creating an enormous trench which for the most part was filled in with the water of the ocean. This was how the Red Sea was born, a body of the water with wholly peculiar features, which is considered to be an ocean in the process of formation. In fact, the tectonic movement separating Asia from Africa is continuing to this day, at a rate of about 1.5 centimeter per year.
The climate
In general the Red Sea climate is hot and dry. Because of it’s latitudinal configuration it has
characteristics that vary from area to area, but on the whole the temperatures ranges from 20C to 30C. As far as the gulfs of Suez and Aqaba are concerned the maximum temperatures are in the June –August period 45C and the minimum never below 15C are in January and February .
The air humidity level is higher in the summer and decreases in the winter.
The winds and breezes The seasonal activity of the wind is especially evident in the central and the southern sections of the Red Sea. Here the northeast winds in the winter and southwest in the summer are the influences of monsoons (periodic winds characterized by clear typical seasonal inversions in the tropical zones).
As for the northern area of the Red Sea the prevailing winds blow all year long from a northerly direction becoming stronger in the winter and tending to calm down in the afternoon and at night.
Waves Waves are a phenomenon of motion transfer caused by the winds effect upon the surface of the water, the height of the waves, that is, the distance between the crest and the trough, depends on three factors: the force of the wind, the duration of the wind activity and the amount of open space for the wind to act.
The ratio between the length and height of waves is approximately 7:1. n other words ,if the wavelength is seven meters, the height will be one meter.
Obviously the diver who goes too close to the coral reef with breaking waves risks being thrown against it with serious consequences.
Currents and tides
There are two types of currents: seasonal currents and tidal streams. Seasonal currents are influenced by the monsoons and the fact that due to evaporation in the summer months the average level of the waters of the Red Sea descends about 70 centimeters. This mass loss of water is compensated during the winter months by an influx of water from the Indian Ocean.
Such currents therefore move in a N-NW direction in the winter months (November-April) and in the opposite direction in the summer months (May-October). It is estimated that a period of 20 years is needed for a total renewal of the waters of the Red Sea.
In the northern Red Sea these currents are weaker than in the central-southern sector, and here the tidel streams, caused by attraction forces from the moon and the sun on the water mass of the oceans, become much more important to scuba divers.
The tide amplitude is directly connected to the phases of the moon: when the moon is full or new, it is on the same axis as the sun: its gravitational attraction is added to that of the sun and consequently the tide amplitude is at its highest (spring tide). When on the other hand the moon is in the first or last quarter its axis is perpendicular to that of the sun and their respective gravitational attractions are opposed: in this case the tide amplitude is at the minimum (neap tides).
The maximum tide amplitude (or spring tides) of this type of currents is about 180 centimeters in the Gulf of Aqaba, with an average surface and running water speed of about 1.5 knots which, in certain cases, can even attain 5-6 knots, equal to 9-11 km per hour. It is therefore absolutely necessary to be well aware of the tidal streams before diving, especially in those areas in which this type of current becomes strongest, such as in the Straits of Tiran and the Straits of Gubal.
If you want to calculate the force and direction of tidal streams you must check the so-called ‘Tide Tables’ published annually by hydrographic institutes in several countries.
These tables list the times of the tides measured at Suez and, in order to be applied to the Sharm el-Sheikh area in the southern portion of the Gulf of Aqaba, this data must be amended by adding a coefficient that takes into account the time it takes the tidal wave to reach the area in question. In the case of Sharm el Sheikh this coefficient is equal to -5 hours and 30 minutes (-6h30’ in summer during daylight saving time). So to find out the exact time of high tide is of the utmost importance in order to be able to swim past the coral reef without any problems when making a short dive. The speed at which the sea level increases or decreases follows a precise mathematical law and is totally independent from the tide amplitude.
Therefore, depending on the time, it is possible to determine not only the exact height of the sea level but also the speed of the current by applying the so-called ‘Rule of twelfths,’
which describes a sinusoid correlating the time to the tide increasing.
Currents, furthermore, tend to be stronger in the vicinity of a headland (in Arabic ‘ras’) and generally in the central points of channels, whereas they decrease in strength in the immediate vicinity of a coastline or reef. Currents present difficulties and potential danger for scuba divers, who should always be aware of them before entering the water.
