Intro; I maintain a list of the longest and deepest caves in the British Isles. I am struggling with one potential "cave".
When it comes to vertical range of a regular cave, it's relatively easy. Change in altitude between the highest point and the lowest point, sump or dry. If the highest point is the roof of a chamber, then so be it.
When a regular cave entrance is huge, breaking out of a cliff face, it's possible that the highest point is the top of the entrance arch (imagine the Grotte de Bournillon's entrance). The highest point that belongs to the cave is used. If the cliff overhangs a long way above a cave entrance, the cave's vertical range does not extend all the way up to that overhang. We're interested in the cave's vertical range here, not the cliff.
So now to the problem; sea caves. There are submerged caves (eg. Mermaid's Hole), there are tidal caves (eg. Otter Hole), and there are wave action sea caves (eg. Sandside Head Cave No. 2). The last type is the difficult one. Sometimes they form blowholes, and the vertical range of those is as easy as a regular pothole. In fact, this gives us the deepest known sea cave in the British Isles; 79 metres, Devil's Limekiln, Lundy Island Sometimes they are taller inside than at the entrance, due to an arched ceiling, and that's easy again. Sometimes the entrance arch is the tallest part, but it's obvious where it starts (eg. Halvikshulen in Norway, at about 80 metres).
But then there's the case where the entrance just keeps curving upwards until it merges into the cliff. Since the cave and the cliff are formed by the same process, there's no obvious point to say where the cave ends, and where the cliff begins. So what is the vertical range? :-\
This comes from a real example, which has the potential to knock Devil's Limekiln off the top spot; the immense alcove in Stookeen Cliff at the Cliffs of Moher, Co. Clare, Ireland. (The one used in Harry Potter and the Half Blood Prince, if that helps.)
By my calculations, the point where it gets a slightly undercutting flat ceiling for the first time is about 95 metres up. But is that really the point where cliff becomes "cave"? Note that the walls extend beyond the upper cliff face, so they can't be used to define a start position.
So is this a cave with 95 metres of vertical range?
And that prompts the next question; does it even deserve to be a "cave" at all? It's an alcove about 40 metres deep. That's less than the height of the opening. Can it really be a cave when it does not even extend into the cliff as far as its own height? Sure, we call it a sea cave, but does it really deserve to compete with Devil's Limekiln, or the likes of Eldon Hole, Sunset Hole and Bull Pot?
Sorry for the academics, but I want the opinion of others here. It's not fair for me to redefine things without the feedback of others.
When it comes to vertical range of a regular cave, it's relatively easy. Change in altitude between the highest point and the lowest point, sump or dry. If the highest point is the roof of a chamber, then so be it.
When a regular cave entrance is huge, breaking out of a cliff face, it's possible that the highest point is the top of the entrance arch (imagine the Grotte de Bournillon's entrance). The highest point that belongs to the cave is used. If the cliff overhangs a long way above a cave entrance, the cave's vertical range does not extend all the way up to that overhang. We're interested in the cave's vertical range here, not the cliff.
So now to the problem; sea caves. There are submerged caves (eg. Mermaid's Hole), there are tidal caves (eg. Otter Hole), and there are wave action sea caves (eg. Sandside Head Cave No. 2). The last type is the difficult one. Sometimes they form blowholes, and the vertical range of those is as easy as a regular pothole. In fact, this gives us the deepest known sea cave in the British Isles; 79 metres, Devil's Limekiln, Lundy Island Sometimes they are taller inside than at the entrance, due to an arched ceiling, and that's easy again. Sometimes the entrance arch is the tallest part, but it's obvious where it starts (eg. Halvikshulen in Norway, at about 80 metres).
But then there's the case where the entrance just keeps curving upwards until it merges into the cliff. Since the cave and the cliff are formed by the same process, there's no obvious point to say where the cave ends, and where the cliff begins. So what is the vertical range? :-\
This comes from a real example, which has the potential to knock Devil's Limekiln off the top spot; the immense alcove in Stookeen Cliff at the Cliffs of Moher, Co. Clare, Ireland. (The one used in Harry Potter and the Half Blood Prince, if that helps.)
By my calculations, the point where it gets a slightly undercutting flat ceiling for the first time is about 95 metres up. But is that really the point where cliff becomes "cave"? Note that the walls extend beyond the upper cliff face, so they can't be used to define a start position.
So is this a cave with 95 metres of vertical range?
And that prompts the next question; does it even deserve to be a "cave" at all? It's an alcove about 40 metres deep. That's less than the height of the opening. Can it really be a cave when it does not even extend into the cliff as far as its own height? Sure, we call it a sea cave, but does it really deserve to compete with Devil's Limekiln, or the likes of Eldon Hole, Sunset Hole and Bull Pot?
Sorry for the academics, but I want the opinion of others here. It's not fair for me to redefine things without the feedback of others.