The question for today...

I ask of you: when does a rock grow up to become a reef? I mean on your charts? Lately I've seen quite a few "rocks" marked on my charts that when they emerge from the water at low tide, or come up looking "white" as you pass them on your beam, sure look like reefs to me. Just sayin....



Jim
Sent from my iPad using Trawler Forum

I've always assumed a rock to be a single rock breaking the surface. A reef on the other had is either multible rocks strung together or one long solid mass of rocks or living reef stretching out along the surface.

Around our area it also might have something to do with the adequacy of the surveys. Small anchorages in the BC central coast aren't high on the priority of the Canadian Hydrographic service.


Jim
Sent from my iPad using Trawler Forum

Interesting question, I guess.
Probably one for a cartographer and I wonder if even they can explain it clearly.

I know what Bill meant and I'm sure he knows rocks and reefs don't always break the surface.

To add to the confusion, they throw in shoals, spits and islets.

The area between Courtney and Lund has all of the above and I doubt anyone can clearly explain the difference.

Bottomline though they all mean WATCH OUT!

My question to you; when does a scuttled destroyer transition from garbage to reef?

From NOAA description of bottom features on nautical charts:

Shoals, banks and bars: Shoals are shallows that constitute offshore hazards to navigation. They are defined as having a depth of 10 fathoms or less and may be composed of any material except rock or coral. A shoal may be an isolated feature or part of a shoal area composed of two or more shoals. A bank is an area of relatively shallow water which is, however, of sufficient depth for safe navigation. Bars are ridges of sand or gravel, often at the mouth of a river, which may obstruct navigation. Note that shallow areas of rock and coral are charted as ledges and reefs and labeled, rather than being delineated solely by depth indicators.

So from what I understand... rock or reef, no difference

JDCAVE said:

Lately I've seen quite a few "rocks" marked on my charts that when they emerge from the water at low tide, or come up looking "white" as you pass them on your beam, sure look like reefs to me.

Click to expand...

A Reef never emerges from the water.

A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Reefs may be up to 261 feet (80 m) below the surface.

A Reef may have a rock contained within it. The reef may even have a rock which is exposed or temporarilly exposed, however a Rock itself is not a Reef. So as Capt Bill was saying a Rock would probably be denoted as a rock or an "*" on the reef. The reef itself would be an unseen hazzard to navigation.

A Shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water to near the surface. Often it refers to those submerged ridges, banks, or bars that rise near enough to the surface of a body of water as to constitute a danger to navigation. Shoals are also known as sandbanks, sandbars, or gravelbars.

Lou_tribal; said:

A shoal may be an isolated feature or part of a shoal area composed of two or more shoals.

Click to expand...

Yup.
Clear as MSCy.

So from what I understand... rock or reef, no difference.

Click to expand...

Reefs can have rocks but rocks can't have reefs. Except, aw never mind; who started this anyway?

Shrew said:

A Reef never emerges from the water.

Click to expand...

Somebody forgot to tell the reefs of the world that.

Well, Capital Bill, up here the Government commissions private rigs called Cooper Catalina reef trimmers. You see them regularly on the coast clipping the tops offa them pesky pinnacles.

Hawgwash said:

Well, Capital Bill, up here the Government commissions private rigs called Cooper Catalina reef trimmers. You see them regularly on the coast clipping the tops offa them pesky pinnacles.

Click to expand...

Well you Canadians are a progressive lot. And safety conscious.

What if the reef is made of hard rocks and the rock is made of soft coral? Ok I am totally lost and off topic now

Lou_tribal said:

What if the reef is made of hard rocks and the rock is made of soft coral? Ok I am totally lost and off topic now

Click to expand...

Reefer madness.

I think what Jim is asking about is the difference between something charted as an isolated rock hazard, but is actually a much larger hazard that may just be topped by a rock.

With good charting the full extent of the hazard/shallow would be charted, but we all know that doesn't always happen. I just encountered one the other day, in fact. The chart showed clear water right up to the shore line. I poked in a way and when the bottom started coming up, tuned, went back out a ways, and dropped the hook. An hour or two later as the tide went out, a rock surfaced not very far from where I made my turn. And a couple hours after that a huge rock reef was exposed extending to within a boat length of where I turned, and where I still had 70' of water. And the whole thing was completely uncharted. Not even the pinnacle rock.

Exactly my concern, Peter!


Jim
Sent from my iPad using Trawler Forum

JDCAVE; said:

Lately I've seen quite a few "rocks" marked on my charts that when they emerge from the water at low tide, or come up looking "white" as you pass them on your beam, sure look like reefs to me.

Click to expand...

Can you point to a few?

JDCAVE; said:

Around our area it also might have something to do with the adequacy of the surveys. Small anchorages in the BC central coast aren't high on the priority of the Canadian Hydrographic service.

Click to expand...

Why I asked

Reefs are made of coral. Doesn't matter whether they come out of water at low water or not.

Rocks or ledges are made of rocks or bedrock.

Just wait until the Cascadia or recently discovered north coast mega thrust earthquakes pop off...what's now 3' above the high tide line could be intertidal

Wxx3 said:

Reefs are made of coral. Doesn't matter whether they come out of water at low water or not.

Rocks or ledges are made of rocks or bedrock.

Click to expand...

My wife corrected me in a similar way. But interesting to see that the chart definitions others have quoted, which I *think* are directly from the chart makers, use the term "reef" more broadly, and seemingly incorrectly.

twistedtree said:

My wife corrected me in a similar way. But interesting to see that the chart definitions others have quoted, which I *think* are directly from the chart makers, use the term "reef" more broadly, and seemingly incorrectly.

Click to expand...

A fascinating topic; reefs.
And I'm sure this isn't where Jim was going when he asked.

Much is written about reefs but, not much is written about reefs.

A statement as confusing as the question; "what is a reef?"

The National geographic Society
http://nationalgeographic.org/encyclopedia/reef/
says; " Natural reefs are made of rocks or the skeletons of small animals called corals. Reefs can also be artificial—created by human beings."

The Department of Earth Sciences, Carleton University, Ottawa
http://hoopermuseum.earthsci.carleton.ca/coral/WREEF.htm
agrees; "The formal definition of a reef is a ridge of rock or shingle or sand at or just below the surface of the water."

Then we get The University of Puerto Rico, Mayaguez
http://geology.uprm.edu/Morelock/concept.htm
confusing the issue when writing about corals, and true reefs by saying; "The primary disagreement concerns the concept of framework in reef building."

But good old Wiki
https://en.wikibooks.org/wiki/Historical_Geology/Reefs
comes to the rescue with the best answer to our discussion when it asks and answers "What is a reef?"

"A reef, to a geologist, is what you get when macroscopic organisms which secrete skeletal matter (hard corals, for example, or oysters) grow on top of one another, forming a mass of skeletal material in relief from the sea bed.

Since the skeletons of reef-forming organisms are invariably made of calcium carbonate, reefs are by definition limestone.

Note that this definition of "reef" is different from that which would be used by sailors, to whom a reef is any submerged hazard."

or a way to reduce the area of a sail

Ted

You guys are making this harder that what it is. Knowledgeable and articulate people often refer to a "coral reef". The qualifier "coral" in this case would be superfluous if the only reefs were, by definition, created from coral.

There are reefs that are created by organisms other than coral such as sponges and algae. These are clearly reefs and clearly not coral reefs.

Finally, a reef has long been considered by mariners to be any ridge like obstruction at or below the surface of the water. This can be rock, sand, shingle, and yes even coral.

You tropical guys need to get out more. ;-)

dhays; said:

You tropical guys need to get out more. ;-)

Click to expand...

Has global warming shifted the tropics way north?
Me thinks CaptBill is the only poster here even close to the tropics.

Hawgwash said:

Has global warming shifted the tropics way north?
Me thinks CaptBill is the only poster here even close to the tropics.

Click to expand...

Very true. Of course, with my cold blood I consider anything South of Santa Barbara as "tropical". lol