Know Your Neighbours: East and West

August-September 2005

This is an article from WaveLength Magazine, available in print in North America and globally on the web.
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By Bryan Nichols

As WaveLength spreads eastward, more paddlers from both sides of the continent are reading about each other. Are Westerners different from Easterners? I’ve lived on both coasts and even recently married an Easterner, so I could wax poetic about the differences, but I’d probably better stick to the geology. No matter what you think of the people, the East and West coasts of North America are very different geographically.

ARE YOU ACTIVE OR PASSIVE?

If you’re a coastline, it depends on how close you are to an active plate boundary. Plate boundaries are the zones that divide up big chunks of the earth’s crust. Those chunks (called plates) are creeping around, which is a notion scientists only came to grips with in the 1960s. You’ve heard of ‘plate tectonics’, right? Continental drift? Even if you’re not familiar with those grand concepts, you’ve heard of earthquakes, volcanoes, fossils and tsunamis—all things that plate tectonics help to explain. For now we’ll just say that the surface of the earth moves, mostly in fits and starts, and plate boundaries are where the action is.

North America has one active coast and one passive one, and you don’t have to watch the news for too long to figure out which is which. Right near shore, the oceanic Pacific plate is either sliding under (subducting) or slipping past the North American continental crust. That makes for a relatively narrow continental shelf, fresh mountains forced upwards, plenty of earthquakes and a line of active volcanoes sprinkled inland a bit, as magma from the subduction zone bubbles upward. Naturally, the crust can’t be going down everywhere, or the earth’s surface would be shrinking. Where does new stuff come up? One area is the Mid-Atlantic Ridge, a spreading center that is (not surprisingly) way out in the middle of the Atlantic. Geologists consider our East Coast to be passive, because that plate boundary is a long way offshore. In the east, the continental shelf is broader and the near shore not so steep or deep.

GOING UP? OR DOWN?

One of the things that really influences the nature of a shoreline is whether or not sea level has been going up or down recently. Since ‘geologists do it slower’, recently might mean within ten thousand years. Thanks to these geological ups and downs, paddlers used to one side of the continent will find that the coast can be very different on the other. The West Coast is usually emergent—that is, the land is emerging or rising from the sea, thanks to uplifting as that Pacific plate slides under the continent. Emergent coasts are also common in polar areas where the land is still rebounding after losing the weight of departed glaciers. Paddling along an emergent coast, you’ll often see signs of previous beaches high above the water. Once you realize what to look for, you’ll spot the same sort of cliffs and platforms that the waves are presently carving—just higher up, more eroded and possibly overgrown.

Submergent coasts are more typical in the Northeast, and sound like what they are—areas where the sea has flooded land that was previously high and dry. Submergent coastal areas (like Acadia National Park) have unpredictable coastlines with plenty of the hills (islands) and valleys (deep spots) typical of land. They also tend to have large estuaries—look at a map and you’ll see that features like Chesapeake Bay make more sense if you think of them as former river valleys that have been flooded by the sea.

Geology, like life, tends to be complicated, and scientists are realizing just how much sea level has gone up and down in the past few million years. It’s an ongoing thing—New Orleans really is sinking, thanks to the sediment load from the Mississippi and all the oil we’ve been sucking out of the Gulf of Mexico. But most sea level change is caused by the comings and goings of ice ages. It takes a whole lot of water to make all those glaciers, so at the height of an ice age, the sea level can drop all the way down to the edge of the continental shelf. This occurs in fits and starts, so many coastal areas in North America show signs of both submergence and emergence.

Whether active or passive, emergent or submergent, this outing we’ll look at ten differences between the East and West coasts. Geology helped shape them—now it’s up to you and your kayak to notice.

© Vancouver Island biologist Bryan Nichols did just marry an Easterner, a Southern Belle at that. The earth moved when they met.

Comparing The Coasts

SHALLOW WATER Uplifting shorelines and subducting plates make for steep, rocky terrain. Western mountain ranges are tall and the coast is abrupt, often with deep fjords slicing into it. On the East side, the mountains aren’t close and all that flat land near the water carries on underneath it, forming extensive shallows. That’s not so good in a deep keeled sailboat, but it makes for all sorts of interesting areas accessible by kayak.

SEDIMENT SIZE Active coasts are steep and rocky, and that makes for big, chunky sediment. Sure, you’ll find sandy beaches on the Pacific, but you’ll also come ashore on pebbles, rocks or even boulders. Western sediment is often still jagged, just recently dumped by rivers roaring down from the mountains nearby. On the East coast you’re more likely to find small sediment—sand, silt and mud that has been leisurely transported by wide, slow moving rivers.

EXPOSURE From Baja to British Columbia, the deeper drop of an active coast means there isn’t much offshore to keep the mighty ocean from thundering onto the beach. This is especially important for sea kayakers—you have to be skilled and well prepared to venture out into swell and surf. Though the Atlantic can be at least as rough as the Pacific, the East Coast isn’t so exposed, thanks to our next item.

BARRIER ISLANDS Barrier islands are aptly named, and very familiar to paddlers from the Gulf of Mexico, around Florida and right up to New England. Formed from sediment, they tend to be long, narrow, relatively low, and sandy. For paddlers and other boaters, they protect large wetland areas and the Intracoastal Waterway. Their presence is perhaps the single most noticeable difference between East and West Coast paddling.

PLANTS ARE LAND On the West Coast, the shoreline tends to be solid, rocky and distinct. On the East Coast, especially towards the Southeast, the shoreline is often defined by vegetation—and only vaguely. Marsh grasses or mangroves often mark the transition from ocean to land, and both can be very soggy. Though marsh and mangrove are interesting to explore, getting lost is easy and it can be hard to find a place for lunch at high tide, when sea water ventures well past the “edge” of the vegetation. At low tide, it’s hard slogging across the muck to a more solid shore.

CAMPING SPOTS As you might have guessed, the geology of the coast has a profound effect on what sort of camping (or lunch) spots you’ll find as you paddle. The steep areas of active coasts can be a problem—often we’ll paddle along insurmountable cliffs in the West. In the East, you might run into the opposite problem—the land is so low that it’s soggy everywhere. Either way, you often find the best camping spots by watching for trees—certain types are associated with the best camping real estate.

ESTUARIES One advantage of a flatter coastline is that a paddler on the ocean can head upriver and go a ways—a long ways, in many cases. Eastern estuaries can be immense, like Chesapeake Bay or Tampa Bay. The rivers that feed them tend to be slow and meandering, allowing a kayaker to explore far upstream. Estuaries are also some of the richest ecosystems around, combining wildlife from the ocean, rivers and land.

MORE PEOPLE People like estuaries as well, and have lived on them for millennia. Steep, rocky shorelines can be difficult to build on—the gentler terrain contributes to the fact that there are more people in the East, which can be good or bad, depending on what sort of paddling you like to do

CHARTS ... OR PHOTOS? Charts are essential on the West Coast, where tidal ranges are predictable and rocks jut up from the depths. Out east, I find myself using aerial photos at least as often. Photos show things that charts often don’t, like channels through the mangroves or marsh that only a kayak can navigate. Thanks to the extensive shallows, they usually show bottom features like sandbars and deeper cuts as well.

VOLCANOES GLACIERS & ICEBERGS (OH MY) Charts are essential on the West Coast, where tidal ranges are predictable and rocks jut up from the depths. Out east, I find myself using aerial photos at least as often. Photos show things that charts often don’t, like channels through the mangroves or marsh that only a kayak can navigate. Thanks to the extensive shallows, they usually show bottom features like sandbars and deeper cuts as well.