PrintThis week, we feature four GeoClips, all created while Dr. Alley was on vacation at the Cape in the summer of 2005. These four "home movies" provide a bit of insight into the origins of the Cape, and the forces that are continuously at work changing our coasts, shorelines, and seas. Shooting and editing credits go to Dr. Alley's wife, Cindy.
As before, we hope you enjoy these, and find them to be useful complements to the readings, class notes, and slide shows of Unit 8.
The Can
Human impacts on the land are easy to see. We have changed the oceans greatly, but the water covers our tracks. In "The Can," Dr. Alley briefly reflects on some issues of the oceans, as he watches one of the less-beautiful pieces of the Cape Cod National Seashore.
A beautiful, natural morning at Cape Cod. But if you turn to the sea, you can see that the evening revelers were there. I've been to the beaches of Greenland. I've been to the beaches of Antarctica. And everywhere I've been, the flotsam and jetsam of humanity are on the beach.
Oceanographers have traced the currents of the Pacific using shoes and rubber ducks that fell off of ships. More importantly, we've probably taken 90% of the big fish out of the ocean. We don't know what an ocean ecosystem should look like because it isn't natural anymore. We've changed the thing. We've put so much fertilizer into the ocean and places from runoff from farming and pollution and sewers that cause huge poison blooms that essentially kill the life when they rot. And taking care of the ocean is a big deal. And it's a deal we need.
The Marsh
Many of the ocean’s big fish, and other denizens of the deep, rely on salt marshes as nurseries and in other ways. But, we are losing salt marshes in many places, as sea-level rise forces the “outer beach” toward the shore, but humans don’t allow the inner side of the marsh to expand into our yards or parking lots. Obvious answers are not easily available, but Dr. Alley frames the question in this next short film clip as he paddles one of the family kayaks on the Nauset Marsh of the Cape Cod National Seashore.
Beautiful morning for a paddle. The tide's coming in, and a really happy professor is going out to see who's running around in the salt marsh, the Nossett Marsh in Eastham on Cape Cod. This is a place for birding. This is a place for shelling. These sand pipers are out getting breakfast.
Salt marshes are remarkably productive places. They are the nurseries of the fish and the shellfish. They're the nurseries of the ocean. They, too, need care.
The outer beach is coming in as the ocean rises. But the inner side is often hardened by humans and not allowed to move. And if we're not careful, we won't have these nurseries.
The Feet
Waves move immense amounts of sand, primarily up and down the beach, but also with a little motion along the beach and eventually off into deep water. In "The Feet," Dr. Alley gets cold feet on Coast Guard Beach, Cape Cod National Seashore, to show you moving sand.
Great Outer beach of Cape Cod, facing the Atlantic Ocean. Early morning. A lone figure leaving footprints on the sands of time. And you will see that, indeed, the waves move lots of sand. As the waves come in and out, and in and out, they keep moving sand ceaselessly, relentlessly. Notice the foot is on top of the sand when the wave comes in.
The foot is getting really cold, because that water is just straight out of the Arctic Ocean, practically. And now there's sand over the foot. And when the next wave comes, and the one after, you will see that indeed, the waves are moving sand in, out, in, out.
As they do so, they sort it. Little pieces are taken out to deep water and lost. Big pieces are not moved at all. And the in-between ones are swirling around the foot. And then another wave comes in, and then that one is really cold. And the hairy-legged sole here is soon going to be buried under the sand. And you can see how much sand is moved in just a couple of waves.
Meet Peat!
Cape Cod is a gift of the glaciers. The numerous kettle ponds left by the ice contribute to the biodiversity of the Cape, but are slowly filling in with sand, peat, and other things. Many of the ponds have already filled, and a walk along the rapidly eroding outer beach often reveals where the sea has cut into one of these filled ponds. In this next clip, Dr. Alley shows one such exposed, filled kettle pond, just below the old Coast Guard station in the Nauset region of the Cape Cod National Seashore.
We're on the outer beach at Cape Cod at Nauset, and we're looking at where the ocean has been cutting back a little bit of the bluffs to reveal what's behind. Now, most of the Cape is sand and gravel. It's outwash from the glaciers from the Ice Age. But what we see here is the filling of a lake. A block of ice fell off the glacier, was buried in sand and gravel, and then melted out to leave a little spot, a lake, which is filled with peat that you see here. The peat is the remains of dead plants. And if you look very carefully, you will see within the peat many of the dead plants.
On top here are grasses of the modern world, but they are not down in the material. Lakes die. They fill with this stuff. When you see a lake on the landscape, you should ask yourself, why is this here? Because something recent has happened to make the lake.