Why Was The United States Underwater?

Several months ago, I wrote about the fossil my son found and what it most likely was. What I didn’t talk about in either article was the trip we took to the Trammel Fossil Park here on the north side of Cincinnati. It’s really just the exposed rocky side of a hill, with signs posting the various stratigraphic layers so you know where you’re looking and other signs showing you the fossils you’re likely to find at each level. There’s no cost to go, and you’re allowed to keep any fossil-bearing stones you find that you care to haul down the hill and back to your car. I found some brachiopods.

My son was extremely disappointed with the trip, at least for the first ten or fifteen minutes we were there. We’d told him we were going fossil hunting, after all, and he wanted to find a Tyrannosaurus rex skeleton. Which, lets be honest, would have been extremely unlikely even if the park had exposed strata from the Albian. But he was six at the time, and he wanted a dinosaur. So I reminded him that the layers we were looking at were from an ocean, because Ohio was underwater at the time.

I don’t think he asked today’s question at that point, but it helped inspire it. Because, eventually, he asked me this: “Why was the United States underwater?”

Well? Why?

Uhm. Something to do with plate tectonics, I guess? And maybe changes in climate?

Can you do better than that?

Of course I can. This’d be a pretty lame blog post, otherwise.

What are plate tectonics?

That’s a great question, and to understand it we’ll need to cover the structure of the Earth itself. The Earth is comprised of multiple layers, rather like an onion. These layers are the:

  • Lithosphere: the outermost rocky shell of a rocky planet (our own, for instance).
  • Asthenosphere: the hot, viscous layer that the lithosphere floats on.
  • Mesosphere (or mantle). Geologists have an explanation for why this is distinct from the asthenosphere and the outer core, and it has something to do with temperature and pressure causing one type of mineral to decompose into another type of mineral. I didn’t quite follow the explanation, and I think I’ll save trying to understand it for the day when my son asks “what is the mesosphere?”
  • Outer Core, a sea of liquid iron and nickel.
  • Inner Core, an extremely hot ball of (mostly) iron and nickel kept solid by pressure.

The lithosphere is the layer we live on – the high parts are the continents and the lower parts are covered with water. And it isn’t a solid shell. It’s broken up into (depending on who you ask and the definitions they use) seven or eight major tectonic plates and a bunch of minor ones. And the plates move.

Why do they move?

The tectonic plates move because the Earth is hot.

Let’s start with an analogy. When you boil water, you get an uneven distribution of heat Heat rises, after all, but the source of the heat is at the bottom. So the hot water rises and the cool water sinks. But then the hot water at the surface cools and sinks, and the cool water at the bottom heats up and rises. This gives rise to something called convection currents. this effect isn’t limited to water, though. All liquids do it – our atmosphere, for instance (which functions a lot like a liquid).

The Earth, when you get below the lithosphere, is pretty much a liquid as well. The mesosphere has convection currents in it, and the tectonic plates can be thought of as the “cool water” part of the current in the boiling water analogy. Magma pushes up from the mesosphere into the lithosphere at the Ocean Ridge (a planet-circling chain of mid-ocean ridges), pushing and expanding the plates. The plates then sink back down towards the mesosphere at subduction zones. These currents also push around the solid chunks of the lithosphere, in much the same way that ice cubes floating in boiling water will be pushed and shoved around.

Now, even the “minor” tectonic plates are massive structures. So, when they get moving, there’s a lot of force built up. When they collide, something has to give. And frequently, what gives is the structure of the plate itself – it will buckle and crumple, throwing up mountain ranges and pushing parts of the plate below sea level. If water, in the form of the oceans, gets access to that portion of the plate below sea level, it will begin to fill the depression. That’s what happened in the theorized Zanclean Deluge, for instance. 5.33 million years ago, the Mediterranean was a depression in the Eurasian plate (bordered by the African and Arabian plates) that was below sea level. It had been a sea previously, until shifting plates cut off access to the Atlantic and the waters dried out. Then the plates shifted further, access to the Atlantic reopened, and the basin refilled in a period of approximately 2 years (with water gushing in at a flow rate 1,000 times greater than that of the Amazon River).

So. Plate tectonics is the answer?

Not completely.

Really? What else is there?

There’s changing climates. See, the Earth was – on average – a whole lot warmer back before the continents had moved into the form we’d recognize today. At present, our average global temperature is about 60 degrees Fahrenheit. During the Paleocene-Eocene Thermal Maximum (55-56 million years ago) the average got up to about 73 degrees F – there were no ice caps at the poles then, and there were palm trees and crocodiles above the attic circle.

Now, estimates are that if the ice caps melted then global sea levels would rise about 70 meters. So that’s not really enough to make an ocean out of (say) the Great Plains, although it would completely reshape the coast and drown Houston and New Orleans. But since the plates were buckled differently back then, the extra water would have increased the odds of flooding taking place.

But, ultimately, North America being underwater had far more to do with plate tectonics than changes in climate.

Oh, as a bonus, the Paleomap Project has a series of great maps of the Earth in different geologic epochs. Here’s what the Earth looked like during the age of the dinosaurs:

Yep.  It was a different world, back then.

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How Long Would It Take To Drive To The North Pole?

About a week ago, we’re in my car running a few errands. My son is chattering away, happily talking about how Winnie-the-Pooh didn’t really discover the North Pole because he was just pretending. (The Winnie-the-Pooh books are our current bedtime story, if you’re wondering.) Something about the combination of these two facts must have sparked what happened next.

“Dad? How long would it take to drive to the North Pole?”

“Magnetic, or true?” I counter.

“What?” he responds.

The Two Poles

There are two North Poles (and two South Poles as well), the “true” (or geographic) North Pole and the magnetic North Pole. And they do not really match up. So what’s the difference between the two of them? Here’s how National Geographic describes the North Pole:

The North Pole is the northernmost point on Earth. It is the precise point of the intersection of the Earth’s axis and the Earth’s surface.

The North Pole sits in the middle of the Arctic Ocean, on water that is almost always covered with ice. The ice is about 2-3 meters (6-10 feet) thick. The depth of the ocean at  North Pole is more than 4,000 meters (13,123 feet).

275px-Arctic_Ocean
Here.

The magnetic North Pole is a little more difficult to pin down. Why? Well, let’s start by letting NOAA tell us what the magnetic poles are:

Magnetic poles are defined in different ways. They are commonly understood as positions on the Earth’s surface where the geomagnetic field is vertical (i.e., perpendicular) to the ellipsoid. These north and south positions, called dip poles, do not need to be (and are not currently) antipodal.

“Antipodal”, by the way, is your new word for the day. It means:

  1. Geography. on the opposite side of the globe
  2. diametrically opposite
  3. Botany. (in a developing ovule) of or at the end opposite to the micropyle

So why does the magnetic field move? Because it’s produced by the spinning of the Earth’s inner core – a solid iron ball almost as big as the moon and hotter than the sun that spins a little faster than the Earth’s crust in a massive sea of liquid (or, at least more liquid) metal called the “liquid inner core”. So far, so good. Right?

world-pr

Now, the full details of what generates the magnetic field are not understood – a fact that I’m certain makes scientists extremely happy. But, as Natural Resources Canada explains, we do understand the basic concepts:

For magnetic field generation to occur several conditions must be met:

  1. there must be a conducting fluid;
  2. there must be enough energy to cause the fluid to move with sufficient speed and with the appropriate flow pattern;
  3. there must be a “seed” magnetic field.

All these conditions are met in the outer core. Molten iron is a good conductor. There is sufficient energy to drive convection, and the convective motion, coupled with the Earth’s rotation, produce the appropriate flow pattern. Even before the Earth’s magnetic field was first formed magnetic fields were present in the form of the sun’s magnetic field. Once the process is going, the existing field acts as the seed field. As a stream of molten iron passes through the existing magnetic field, an electric current is generated through a process called magnetic induction. The newly created electric field will in turn create a magnetic field. Given the right relationship between the magnetic field and the fluid flow, the generated magnetic field can reinforces the initial magnetic field. As long as there is sufficient fluid motion in the outer core, the process will continue.

So why does it move? well, the magnetic field is created by a fast-spinning ball inside a slow-spinning ball. So it wobbles, at an average speed of 10 kilometers per year for the entire 20th century.

nmppath2001_med

So where is it right now? According to the World Data Center for Geomagnetism you’ll find it at 80.4° North, 72.6° west. Or, in other words, Nunavut, Canada.

Magnetic Pole
Right there

How long would it take to drive there?

According to the handy Computing Distances between Latitudes/Longitudes in One Step page, and checking the latitude and longitude of Cincinnati, Ohio (39.1000° N, 84.5167° W), I get the following figures:

  • Geographic North Pole: 3,524.64 miles
  • Magnetic North Pole: 4,144.18 miles

Now, looking at the map above, you would think that driving to either pole would be impossible. After all, there’s ocean in the way! But this is where living in Cincinnati comes in handy – we have a Ride the Ducks tour here!

duck boat

The “Duck Boat” is a World War II surplus DUKW, an amphibious vehicle capable of cruising at 35 mph (56 km/h) on roads and 4.41 mph (7.14 km/h) in the water with an operational range of 400 miles on land (or 58 miles/93 km in the water). I doubt it has the ring mount for the machine guns, though. So, we can do this. In theory, at least.

Eyeballing the map, I’m going to go with an estimate of 90% overland travel to the magnetic North Pole and 65% overland travel to the geographic North Pole. Further assumptions will be:

  • Driving 18 hours a day – my wife has agreed to go along with this mad idea, so we can drive quite a bit. But we still need to stop for bathroom breaks, meals, stretching our legs, and refueling.
  • We’ll be hitting our cruising speed.
  • We don’t get eaten by polar bears.
  • We’re not worrying about mountains.
  • We drive in a straight line, and we don’t get lost.

Getting to the geographic North Pole is roughly 2,291 miles over land and 1233.64 miles over sea. That’s (2,291/35) + (1233.64/4.41) = 345.19 hours. Based on our assumptions, that’s 19 days, 4 hours, 15 minutes. And we would have needed to stop for gas 27 times on the trip.

Getting to the magnetic North Pole is 3,729.762 miles over land and 414.418 miles over sea. That’s (3,729.762/35) + (414.418/4.41) = 200.54 hours. Based on our assumptions that’s 11 days, 3 hours, 23 minutes. And we would have needed to stop for gas 17 times.

Either way, we also get a complimentary duck whistle for the trip.  So my son is going to love this!

Why Is It A Creek?

Two of my son’s friends live in an apartment complex that has to be reached by crossing a bridge. One day, when we’re going to visit them, my son looks over the bridge and cheerfully announces that “They’ve got a lake!”

“It’s not a lake,” my wife corrects him. “It’s a creek.”

“Why is it a creek?” he asks.

You know what? I haven’t the slightest idea. Growing up I’d heard of rivers, and streams, and creeks, and criks (the latter being a word I’ve only ever heard in Kentucky, and may just be “creek” with an accent). As a child, I’d simply assumed that rivers were big, streams were medium-sized, creeks were small, and criks were really small. Turns out, though, that I don’t actually know. So I turned to the Internet, and ended up at Duhaime’s Law Dictionary.

The dictionary defines a river as: “a watercourse with a current and which is of capacity to be navigated”. Fair enough. So, what’s a watercourse? Well, according to the dictionary, it is “a stream usually flowing in a particular direction, in a definite channel, having a bed or banks, though it need not flow continually”. What’s a stream (), then? “A watercourse having banks and channel through which waters flow, at least periodically”.

Recursion is a popular technique in law, apparently.

The discussion in the definition of “river” muddies the water (so to speak), because navigable doesn’t seem to mean what you think it would mean. I mean, [i]I[/i] assumed that “navigable” means “you can navigate on it”. That is, boats can travel on it. But, in the United States at least, that’s not what it means. 33 CFR 329.4 (Definition of Navigable Waters of the United States) defines it in this fashion:

Navigable waters of the United States are those waters that are subject to the ebb and flow of the tide and/or are presently used, or have been used in the past, or may be susceptible for use to transport interstate or foreign commerce. A determination of navigability, once made, applies laterally over the entire surface of the waterbody, and is not extinguished by later actions or events which impede or destroy navigable capacity.

So, a river is a watercourse with a current that is subject to the ebb and flow of the tide, or that is (or has been) used to transport interstate or foreign commerce. Presumably, then, if it doesn’t cross state lines or feed into the ocean, then it isn’t a river.

But wait! It’s more complicated than that! In State v. Bonelli Cattle Company, the Arizona supreme court stated:

Obviously, a river does not have to flow continuously across the whole of its bed to the high water mark in order to avoid a claim by abutting owners to a part of the river’s bed. The channel of a river is the bed of the stream over which its waters run, Benjamin v. Manistee River Imp. Co., 42 Mich. 628, 4 N.W. 483, and the bed of a river is the space contained between its banks, Pulley v. Municipality No. 2, 18 La. 278.

And in Mogle v. Moore, the California Supreme Court stated:

Surface waters are defined as waters falling upon and naturally spreading over lands. They may come from seasonal rains, melting snows, swamps or springs, or from all of them. Surface waters consist of surface drainage falling on or flowing from and over a tract or tracts of land before 9*9 such waters have found their way into a natural watercourse. (26 Cal.Jur., p. 279, and cases cited.)

A stream is a watercourse having a source and terminus, banks and channel, through which waters flow, at least periodically. Streams usually empty into other streams, lakes, or the ocean, but a stream does not lose its character as a watercourse even though it may break up and disappear. (Hellman etc. Bank v. Southern Pacific Co., 190 Cal. 626 [214 P. 46].) Streams are usually formed by surface waters gathering together in one channel and flowing therein. The waters then lose their character as surface waters and become stream waters. (Lindblom v. Round Valley Water Co., 178 Cal. 450 [173 P. 994]; Horton v. Goodenough, 184 Cal. 451 [194 P. 34]; Gray v. Reclamation District No. 1500, 174 Cal. 622, at p. 650 [163 P. 1024].) As we have observed, a continuous flow of water is not necessary to constitute a stream and its waters stream waters. (San Gabriel Valley Country Club v. Los Angeles County, 182 Cal. 392 [188 P. 554, 9 L.R.A. 1200].)

 

So. A stream is any watercourse with a source, an ending, and a distinct set of banks and a channel. A river, apparently, is just a stream subject to tidal action, or that is used for interstate commerce. But what on earth is a creek? Well, at this point I’m giving up and going to a regular dictionary. Merriam-Webster defines “creek” as:

  1. chiefly British : a small inlet or bay narrower and extending farther inland than a cove
  2. a natural stream of water normally smaller than and often tributary to a river
  3. archaic : a narrow or winding passage

Origin of CREEK
Middle English crike, creke, from Old NOrse -kriki bend[/quote]

So, there you have it. A creek is a stream that feeds into a river. Unless it’s a narrow bay. And so the creek in front of my friend’s apartment complex is a creek because it’s a stream that feeds into a river.