Difference between revisions of "Diving the Cape Peninsula and False Bay/Vulcan Rock"
Latest revision as of 07:57, 25 December 2010
Vulcan Rock is the highest point of a extensive area of granite reef and breaks the surface at some states of the tide. It is low and flat on top and big enough to park a car. If there are extensive whitecaps it may be difficult to see from a distance, so it can be tricky to find on a day with low swell and a strong south easterly wind unless you have GPS. A spectacular dive if the visibility is good.
This site is in a Marine Protected Area (2004). A permit is required.
The exposed rock marking the site is shown on charts of the area as "Vulcan Rock."
Maximum depth is over 30m but this is some way to the north of the rock.
Visibility is variable and can range from more than 20m on a good day to less that 3m on a bad day. A strong south easterly wind will usually move the surface water offshore and cause an upwelling of cold clear water which will temporarily improve visibility. The visibility in such a case may improve overnight, and may deteriorate almost as quickly if the wind stops and there is a day of bright sunshine, which stimulates a plankton bloom, also locally called a red tide. A red tide can drop visibility doen to less than 5m in a day, but in these cases there may well be reasonable visibility below the surface layer, though it will probably be quite dark, and the light very green. Another cause of poor visibility is north westerly winds.
Vulcan rock is the top of a very big granite tor. It is made up of large corestones on top of more of the same, down to at least 25m . There are lots of crevices, overhangs and fairly narrow gaps. Boulders are often several metres high. There is usually a knocking sound as loose boulders are rocked by the swell.
There is a swimthrough/cave directly under Vulcan rock. The bottom is at 18m, roof about 2m higher. There are 4 seperate entrances, none of them easy to see from outside unless at the same depth. The cave is probably between 20 and 30 m max extent, and maybe 20m wide at the widest. Two of the entries are at the edges of the relatively flat floored part, and the other two are across boulder strewn bottom and irregularly shaped. There is also an air cave overhang on the north east side of the main boulder at about 13m depth with a number of small domed pockets in the ceiling which are bare of all growth, showing that there is often air in the overhang.
There are big bolders or pinnacles to both sides of one entrance. The next entrance anticlockwise is at the bottom of a little gully, and has a small cave to the right of the entrance to the main cave.
To the north of the rock is a fairly shallow pinnacle.
Geology: Granite of the late Pre-Cambrian Peninsula pluton
The site is exposed to south westerly swells, which can cause a strong surge. The site is usually at it's best in summer but there are also occasional opportunities in autumn and winter.
This is an area which sometimes has upwellings, caused by strong south easterly winds, resulting in cold clear water, which may develop a plankton bloom over a few days, which will reduce the visibility again.
Keep a lookout for times when the south west swell is low and short period, and there is not too much south easterly wind forecast. The south easterly wind will usually improve visibility, but if it blows too hard, can make the trip out to the site uncomfortable, and the trip back quite unpleasant. What you want is a few days of low south westerly swell with strong south easters in the afternoons, and quiet mornings, when there is very little wind chop and there has not been time for a red tide to develop. For this reason, most dives to this area are scheduled for early launches.
The site is acessible only by boat. it is about 5.5km from Hout Bay Harbour. Anchoring is possible, but the bottom is very rugged and anchors and even shotlines often foul.
Heavy growth of red bait in shallower parts, Some kelp, probably mostly Split-fan kelp, on top surfaces down to about 15m. Heavy encrustation of sponges, sea fans, bryozoans and colonial hydroids on steep faces, and particularly under overhangs. Flatter rock surfaces in deep areas are often covered by urchins and grey cucumbers.
There are several caverns and other holes between and under the boulders. The best known is directly under the exposed rock, at a depth of about 15m. It is large and has several access openings around the sides (about 4) The inner space is about 2 to 3m high in places and is probably over 10m wide and long. The entries are not particularly obvious, and are often missed, though they are quite large.
There is also a "balloon cave", where the roof is a high dome. The position has not yet been mapped, but it is said to be to the east of the exposed rock, and at a similar depth to the main cavern. The balloon cave will trap air, which if allowed to accumulate, will kill the invertebrate growth on the roof, so try not to breathe inside this cave. It will be dark inside, so a light will be necessary to see the growth on the walls and roof.
Good site for photography, specially close-up shots of invertebrates.
Choose a route to suit your desired profile. For greater depth go north past the north pinnacles which do not break the surface. There is a large swim-through under the main pinnacle at about 18m depth.
Cold water, Strong surge in cracks and swim-throughs. Sea urchins. Strong offshore winds may develop over a short time, making it tricky to spot divers on the surface, and a wet trip back.
No special skills required, though the ability to deploy a DSMB is useful in case you are separated from the group or need to surface away from the shot line.
The site is cold and relatively deep, and a dry suit is recommended. This is a dive site where the use of Nitrox can be worthwhile to extend no-stop time. A reel with DSMB, Light and Compass are also recommended.