Sea Level

William Kent
May 17, 1977


What an illusion geography is. In school we are taught about continents and oceans, mountains, islands, valleys, lakes, rivers and bays as though they were immutable and distinct concepts. They provide for us a very permanent frame of reference, very necessary for us to conceive of "where we are".

In the scale of magnitude of the earth’s geography, a difference of a few hundred feet is insignificant. Yet suppose that sea level were to change by just that much! That would only be a change in ocean depth of a fraction of one percent. Proportionally, we are accustomed to even greater variations in the depths of reservoirs, lakes, and rivers. Why not the oceans?

Bays might become lakes, and vice versa. A chain of islands, like Hawaii, might become a single mountainous land mass. We couldn’t write in our geography books that Hawaii consisted of a certain number of islands -- it might change with every 50-foot shift in sea level.

Mountains could become offshore islands, and vice versa. Inland valleys might become bays, or lakes, or coastal passages.

The very idea of memorizing the shapes of islands and continents becomes nonsense. The shapes that are so familiar to us are mere accidents of the water level. Raise or lower that by a few feet, and the cross-sectional profile becomes entirely different. North America might extend to include the continental shelf. Hudson Bay and the Gulf of Mexico might disappear, and there might no be such an obvious separation from South America. Or, in reverse, North America might shrink to its westernmost 1000 miles, with the Appalachian "Islands" 1500 miles out to sea!

(I don’t know the actual shapes and depths involved. It’s the idea that matters, not the specific facts.)

Water management in the West gave me my first experience with these illusions.

When I stand on the shore of a lake, I have a comfortable feeling at "ground level". It is a horizontal world. It is totally different from standing high on a mountainside, with a great vista spreading out below, perhaps a valley. Then I am aware of being far above "ground level", and there is a subliminal, barely felt anxiety that the possibility of falling exists here.

The two are totally different experiences, mutually excluding each other. Except when it comes to reservoirs. In the West, I’ve had the opportunity to see new reservoirs filling up, transforming a cliff-hanging mountain road into a lakeshore drive. The ground level has been moved by the engineers, coming from "down there" to "up here".

And in this year of drought, we’ve experienced the reverse. Ground level has moved back "down there"; lakeshore becomes hillside. That exciting little offshore island, the tempting target of a swim or boat ride, the private haven for fishing or picnicking -- becomes just a dried up little hillock, hardly worth noticing at all. Lake bottoms are, in my mind, murky places occupied by fish, slime, and esoteric plant forms. But drought reveals trees down there, and the remains of cabins, fences, roads, and bridges. There’s a clash in my head: those things belong on land, and don’t fit into my picture of the bottom of a lake.

The most direct strain on my brain, though, comes from standing on a dam. Then my senses have to reconcile two opposite simultaneous experiences. On the one side of this thin, artificial divide, I am high above a valley. On the other, I am down at water level.

My brain wants to think of "ground level" as being uniform. Yet I am at the same time at ground level and high above it. My brain wants to think of lake and valley as quite different phenomena. It doesn’t want to accept the fact that both sides are the same, that somebody has simply erected a thin barrier across the valley, filling one side with water but not the other.

It’s all an accident of water level. Our fixed notions of the shapes of geographic features, and what kinds of objects they are (like mountains or islands), would be changed dramatically by trivial variations in water level. When I, totally naive about geography and geology, contemplate the dimensions of the universe, and the earth, and the oceans, it seems absolutely miraculous to me that sea level is as constant as it is. In the grand scheme of things, a change of a couple of hundred feet in sea level looms as trivial as the proverbial drop in the bucket.

All our different ideas about continents, islands, mountains, etc., are just accidents of the momentary interaction between land and water. Those are the only two real distinct concepts in this geography: land mass and water. Our notions of what things are, and where they are, and their shapes, just depend on where the waterline is at the moment.

I can’t even begin to speculate on the total mental chaos that would result from an abrupt change of several hundred feet in the sea level. I don’t mean the obvious physical problems of flooding and so on. I mean the sudden disorientation of being in an alien landscape, all the fixed points of reference suddenly gone, replaced by entirely new and unfamiliar features. It’s just a simple change in the waterline -- but what a psychological trauma! What an upheaval of our basic frame of reference! A mid-westerner would suddenly be at the seashore, a mountain-dweller would be on an offshore island. It could be as psychologically unsettling as the stable earth suddenly shifting giddily under our feet in an earthquake.

And even more interesting to speculate on: how different would our lives be if such large fluctuations in sea level were regular and normal occurrences, like the tides? What would happen to our concepts of place, and geography, and boundaries, and landmarks? How might we accommodate to shorelines which shifted hundreds of miles back and forth periodically, rather than the few feet we now experience with the tides? I’ll leave you to contemplate these.

How much our view of life is conditioned by the fragile stability of the level of the sea!