Tasmania – A West Coast Beach
As a contrast to the calm, protected, shell-covered Seven-Mile Beach, the next day we went to one of the beaches on the west coast. The contrast was striking.
While there was sand, it was only where it was protected enough by rocks to keep it from being swept away. And there were hardly any shells.
See, here’s the difference: Tasmania is smack in the middle of the “Roaring Forties”. The prevailing wind is from the west, and if you go west from Tasmania, the first land you hit is Argentina, about 3/4 of the way around the planet. This means that the wind is blowing over one of the longest uninterrupted stretches of ocean in the world, and because of the lack of obstructions it can regularly really wind up to some serious gales[1]. And the beaches on the west side of Tasmania are fully exposed to this. So, any loose shells or unattached animals don’t just get broken by the waves, they get ground to a fine organic paste over a fairly short timespan.[2]
This is all that was left of a good-sized crab. I suspect that it was dropped after some bird ate it.
We found a few of these odd little mollusks, which survived the wave action by sticking to rocks.
The shell was flattened on one side so that they could hang on.
Looking at the flat side, the spiral pattern looks like some kind of snail, although we couldn’t actually see anywhere that the animal could get out.
We found a sea urchin, too. These are a lot less brittle than a regular seashell, and can apparently bounce around a bit without cracking open.
And this short-armed starfish was hanging on to the side of a little tidal pool, and was stuck firmly enough that wave action would be unlikely to knock it loose.
So, basically, here on the windy side of the island, the only things that survive on the beach for more than a couple of days are things that are either very durable, or that can stick to the rocks like glue.
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[1] The day we were there was about as calm as it ever gets, and there was still a pretty stiff breeze. On one of my previous visits to Tasmania, I got to tour the Cape Grim Weather Station just up the coast, and right around noon a storm rolled in and I got to watch the anemometer readings spiking up around 120 kilometers/hr (about 60-70 miles/hour), while the whole building vibrated. I asked one of the guys there about this, and he shrugged and said, “Oh, this usually happens once or twice a day this time of year”.
[2] The stench of rotting kelp and shredded marine life gets pretty overpowering. “Salty tang of the sea”, my foot.
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Lovely- but are you ever coming home?
That must really be something. Here in San Diego, the next thing west of us is Miyazaki, Japan, 6000 miles away and we don’t get those kinds of winds at all.
KT: The latitude has a lot to do with it, too. At 40 degrees South, Tasmania is also smack in the middle of the southern Westerlies wind band, where the prevailing wind from the west is strongest. San Diego, on the other hand, is at 33 degrees North, where the winds are switching from being the westerlies to being the easterly trade winds, and so are weaker and more variable in direction(the “horse latitudes”). It looks like there are some other factors too. When I looked up average wind speed maps for the US and Australia, the US west coast is fairly calm (probably because the Rockies block the wind from flowing across, and so the air piles up in a stagnant mass to their west), while the entire south-western part of Australia has nothing much to block the wind and is reliably windy.
I’ve got three more Tasmania-related postings to go, and then we’ll be back to Michigan. With a very nice, colorful leech!
Someone I know found some of those flat sided shells while on Wake Island. They gifted them to me and me being the marine enthusiast and scientist that I am, I was really confused by the design. I could easily guess that the flat side was to stick to something, or anchor itself, but for the life of me, I can’t figure out how the creature would enter/exit or even feed while living on the rock or wherever it attached itself.
And I do think that that’s probably what it does because of the lopsided look it has on top, one side being smoothed over more than the other.
And if it’s not what the creature does, the only other thing I could think of was that it was a shell piece that had been smoothed by the current. But that wouldn’t make sense with how level the one side is and especially not on the beach you found yours at if there is such a lack of shell debris and pieces.
Did you ever find out what animal the shell belongs to? Or how it lives?
The flat round shell is called an Operculum. It is the lid/door that turbo/turban snails have.