Rock of the Week #8

EDITED *** WHY DIDN'T YOU GUYS TELL ME I HAD THE FOSSIL WRONG? THANK GOOD NESS FOR STUDENTS (NOW GLOATING STUDENTS). The Rock of the Week #8 contains a Receptaculid. It is maybe a green algae or maybe an echinoid but definitely not a bryzoan!!! Excuse me please. Receptaculids are most prevalent in early ordovician so early Paleozoic is still the correct answer.


For my birthday week, my very favouritest rock type. Note that I had to massively screw with bright/contrast/saturation to make these photos look like the rock really looks! Maybe I shouldn't take pictures of rock of the week after dark in my office while pretending to prep for tomorrow's early lectures. Hm.

Anyway:
1. Name the rounded reddish mineral.
2. Based on the colour (and any crystals if you can find them), what mineral comprises the very fine-grained matrix of the majority of this rock?
3. Rock name or metamorphic grade?




Solution to Rock of the Week #7:

This is a fossiliferous Ordovician (520-430Ma) Kanosh Formation limestone from Crystal Peak, Utah. It is almost completely composed of fossil material, so it would be called a biosparite or biomicrite (Folk classification) or a biograinstone (Dunham classification). Due to the large amount of broken shelly material, this rock is also called “hash”, in this case “brachiopod hash”. There is a wide variety of fossils in the rock, including the very large bryzoan and numerous brachiopod shells. Crinoid stem sections are present as well as lots of little very thin bits looking like fingernail clippings – I think these are part shed exoskeletons from trilobites. This assemblage is consistent with deposition on a shallow marine shelf. The prevalence and diversity of brachiopods, as well as the abundant trilobite fragments suggest lower Paleozoic, as brachiopod diversity and trilobite abundance never fully recovered after the end-Ordovician extinction. As such, this type of assemblage is sometimes called “Cambrian-type” assemblage.

1. (1 pt) What is large fossil?
: 1 point given for bryzoan.

2. (1 pt) Rock type?
: 1 point for either fossil hash, biosparite, biomicrite, or biograinstone.

3. (1 pt) Age:
: 1 point for b) early Paleozoic.

Succulent of the Week - Aloe dichotoma

The beautiful and iconic Quiver tree gets its common name from the indigenous practice of using the hollowed out spongy branches to store arrows. Its original name is Choje (San) and the Afrikaans speakers call it Kokerboom (which means... that's right... quivertree.) These trees, in their natural habitat, seem to have this ethereal air of permanence about them. Although some sources on the web suggest that they are threatened by habitat destruction, I think I can say with certainty that the area I visited has seen very little expansion of human land use for a very long time.

I did hear, anecdotally, that mature specimens are dug up and shipped to places like Dubai and Palm Springs for exotic landscaping. The tree aloes are very slow growing, and it is not possible to grow them in captivity to this size on the timescale of a Dubai construction project. There are rumors of people buying whole tracts of land just to deforest them for export, and the survival rate of the trees in shipment is not fantastic. This is just heartbreaking as this landscape is such a slow and old place, it's easy to imagine that a few greedy people could destroy it very quickly and recovery might never happen.

The species name "dichotoma" refers to the usual 2-pronged branching style. Given that some of the examples I photographed seemed to have more than two branches from some joints, it might be the Bastard Quiver Tree (Aloe pillansii), although that doesn't seem quite fair.


Here's a social weaverbird colonial nest in a large Quiver tree:
These beautiful examples were spotted near NousWells in the Northern Cape, not far off the N7 (if you consider "not far" enough space to get completely stuck, lost, separated from the other vans, without cell phone reception, and running out of beer and ice).

Gittin the Fish - How it works

First you get the net onto the boat. The net is 150 fathoms x 5 fathoms. On top there is a float line and on the bottom there is a lead line. We stacked it on the dock on a tarp and pulled it off with the net reel.
It goes over the bow roller and through the fairleads, which slide back and forth to help wind the net evenly on the reel.

Next you go to the cannery (our relationship is with Copper River Seafoods thus far in the season) or the tender boat and get some chipped ice into the fish hold. The ice lasts quite a while actually. We have a big snow shovel on board for moving the ice around. Note stylish double-funnel day marker.
Then you wait. And you check the Fish & Game website to see whether ADF&G is going to announce an "opener" - usually 12 hours long this early in the season - when you can fish.

Fast forward to putting the net in the water. You tie a big orange buoy to one end and throw it over the bow roller. The bow roller has a hub like a 4wd hub on a pickup. You lock the hub, turn on the bow roller to spin seaward and idle backward for a few minutes while 900' of net rolls off the bow. That's why its "drift net" fishing.
Then you "soak the net" for a while - maybe 15 minutes at first just to check whether you are in the fish. When you're pretty sure you're in the fish, you might leave it an hour or more. You can even drop your end of the net on a second buoy and putter around to the first end to check for fishies.

When you're ready to pull the net, you just turn on the net reel and wind it in. This is a red net so the mesh size is about 5 inches, just the size to catch a sockeye (red) salmon around the gills. They can see the net in clear water but they get frustrated and try to swim through it anyway. When a fish comes over the bow roller you stop the real and paw through the net to "pick" the fish out. Sometimes they get pretty wrapped up and tangled.
You ease the fish out of the net. Those blackish lines on its back are from the net. You see those on fish at the market and you know it was caught in a gillnet as opposed to some other method. Some are dead in the net but most come onto the boat alive and the squirm around and slime you while you work. Raingear is key. You can see my black raincoat is covered with silver scales. Then you reach under the gillplate and pop the artery in there to bleed the fish. This helps preserve the meat.
Sometimes you get lucky and another species, like this king (chinook) salmon will get tangled in the net. Obviously he can't get his head through it but sometimes just his teeth or nose will get caught. Often times one person can stand next to the net roller with a big dipnet watching for kings to make sure they don't fall out when the net comes out of the water. This one was just barely caught but he got pulled over the bow roller and flew into the boat! He's about 19 lbs, a little smaller than average. We sold him for $6.70/lb. You can buy him for about $25/lb.

Here they are on ice in the brailer bag. The bag will get picked up by the crane on the tender boat and weighed and we will get a little ticket that says how much fish we delivered and what kind. Straight to a market near you.

Cordova by day... and later in the day.

Sila and I watched a huge sea otter lolling on the dock during the stormy days we arrived in Cordova. A few hours later, the sun came out and the sea otter gave birth. We called the baby Meep because he squeeked like a toy every time his mama turned him over and over to wash and fluff him.

During the storms, Alaska Department of Fish & Game called the first "opener" for Thursday May 15 on the Copper River Flats. Due to the foul conditions, we waited it out. We were glad of that - abet a little sheepish - because the average catch per boat was ~12 fish and we had calculated we needed 13 to pay our round-trip fuel to the Flats. Over the sunny weekend following, professional net menders like Lisa here were really busy on the docks - everyone anticipating the BIG ONE opener on Monday the 19th. Oh yah, and every next opener is gonna be the BIG ONE.

Here's Cordova Harbor as we first saw it when we pulled into town. It's really a tiny harbor compared to some, but it is home to most of the south-central Alaska gillnetting fleet - usually in the 30' range - so they pack a lot of boats in that small real estate. The town is cozily wrapped around the harbor and has an old-towny feel from its turn-of-the-century spruce sided buildings with big carved wooden signs. Like many wet towns in Southeast Alaska, most of Cordova's storefronts have deep awnings and you can walk around town without getting too wet.
Here's a view from K-float where we docked, looking up to town. And that's pretty much it! You can almost make out the little ski hill above town. They have a chair lift! It was recycled from Sun Valley, Idaho.
Bustling "business district" of First Street, Cordova: picture of cuteness.


And with this view of busy Second Street we conclude our tour of the Business District. Do note that every home and business in Cordova has an absolutely a$$-Kicking view.

Here are a couple of cute houses between the harbor and the cannery row . . . Cordova is an Obama Town.


The old Canneries line the waterfront north of the small boat harbor. Whether active or "historical", they all share the extremely tall, precariously old and rotty looking piling complex from which ice is lowered to boats in big plastic totes or by shooting out of a large hose. More on that later. The docks are well above high tide and maybe even above local tsunami potential. The corregated exteriors hide thoroughly modern processing, smoking and freezing facilities as well as kids from all over the world who come to the Alaska canneries to work for the summer.Not all of those piers are seeing action these days... I think that is somebody's vegetable garden half way down this grass-covered dock but I was too scared of the rotty wood to find out.

The USCG Cutter and buoy tender Sycamore was on hand for the opening of the season, launching random safety checks on the fleet. These fishermen are generally pretty conscientious, and NOBODY wants to miss a day of fishing on account of being short a fire extinguisher or other violation. Hilarity prevailed however, because the marine suppliers in town were universally out of at least the following items:

1. day markers (a black marker in the shape of two cones point to point); required to be shown when fishing during daylight hours.
2. hand-held breathalizers (one for every person onboard required to be produced by captain in case of accidents while underway) ; and
3. the REPORT ALL INJURIES placard that must be displayed in every boat.

The auto parts store, fortunately, had a really large supply of black funnels which were readily formed into a day marker with black electrical tape - maybe not typical but probably legal? An internet search turned up the detailed text of the REPORT ALL INJURIES placard and carefully Sharpied substitutes appeared on bulkheads across the harbor. As for the breathalizers - everyone is waiting for reinforcements from Anchorage.

When the sun started setting on the harbor that clear beautiful evening, the snowy mountains around Cordova lit up with alpenglow. The harbor was like a mirror. Here are a few favorites.






Next post: the fishies.

I was worried I wouldn't like fishing

turns out I frickin love it.


20lb King Salmon, Kokenhenik Bar, Copper River flats, 19-May-2008

Rock of the Week #7

Here's a fun one I collected Long Ago.
1. What is the large fossil (meaning the big round thing on the right side of first photo)?
2. Name this rock (any appropriate classification scheme is OK.)
3. Multiple choice. This rock is:
a) Proterozoic
b) early Paleozoic
c) late Paleozoic
d) Mesozoic
e) Cenozoic
f) Quaternary (modern)




Solution to Rock of the Week #6:

This rock is only 500 years old! It erupted from Panum Crater, a small rhyolitic cone in the Mono-Inyo chain in California’s Long Valley Caldera. Legends among the local Inyo tribe of the Native Americans reveal that the eruptive event was observed by local residents. The Mono-Inyo volcanics are about 76% SiO2, with only rare phenocrysts, producing pumice and obsidian. Both are glassy products but with variable bubble contents. The pumice (like this sample) can be very low density! It can be found floating on nearby Mono Lake. Nobody can resist picking up huge rocks of pumice and lifting them over head.
Here's an example from Tulane's 2002 trip.

1. (1 pt) What is rock?
: 1 point given for pumice.

2. (2 pt) How did it form?
: 1 point for volcanic.
: 1 point for rhyolitic or dome or crater.

Succulent of the Week - Faucaria tuberculosa

This funny little beast is another Eastern Cape native. The gaping leaves of Faucaria give it the common name "Tiger's jaws".

This guy was pretty compact when I brought him home. After several weeks on a mostly "bright shade" windowsill, he seems to be opening up a bit. It's truly amazing to watch succulents adjust to their surroundings over the course of weeks... in both shape and colour.
Although it is fall, I'm afraid the 'bright shade' situation might not be bright enough to encourage this little guy to flower. According to Dr. Internets, it is a good beginner's succulent because it is not as particular as some as far as watering schedule, is less rot-prone and can recover from rot if clean cuttings are salvaged. In addition, it tolerates a wide range of sun conditions and enjoys occasional fertilizer but grows well without it. It's the pet snake of succulents.

in search of Columbia Glacier

Prince William Sound truly is one of the wonders of this world. Can't say we were blessed with good weather during our crossing - but it is gorgeous and sunny as I write from Baja Taco in Cordova, looking out over the blue harbor and snowy mountains - and hundreds of bowpickers.

En route from Whittier to Cordova, we stopped in Columbia Bay behind Glacier Island to try to get a look at Columbia Glacier. There were a lot of icebergs behind Glacier Island and we had to idle up the bay and drive from the bow to watch for ice. There were a lot of happy otters though.
At the mouth of Columbia Bay, there ice fields got so thick that we couldn't get into the bay. We took a side route into Heather Bay and Sila dropped me off in the mud on Moraine Spit. I clambered between the tide-stranded icebergs and mud and tried to get a clear view to the glacier.

The receding tide had left all kinds of strange icey forms on the spit, in shades of blue and white.

With matching seagulls.

Fresh water falling on the sea and flowing off the melting bergs was frozen into a thin sheet of shore ice - which fell also on the falling tide and broke over the rocks on the shore:

In case you ever doubted that ice is hexagonal, look deeply into your screen for gorgeous evidence of volume diffusion creep in glaciers:

We never did get a look at the mighty Columbia. It has receded miles from where it is shown on the 1960's marine charts.

Shrimping at Ester Island

We left the pot in about 400' of water overnight:

When we pulled it up all the cat food was gone from the tins.

But we got our breakfast:

Rock of the Week #6

Anyone who's seen this before in the field will no doubt recognize it instantly. For the South African students though.... I have encouraged them to use google, and a certain locality name is actually written on the rock. We'll see how they fair!

1. Rock type
2. How did it form?




Solution to Rock of the Week #5:

This rock is a Jurassic slate from the Merced Falls Formation in the Sierra Nevada foothills, California, USA. The slates were deposited in a Jurassic-age subduction trench and accreted to the western margin of North America in the late Jurassic. They are very low grade metamorphic (sub-greenschist) and are dominated by the “slaty cleavage” formed by pressure solution. The empty cubic holes are missing diagenetic/metamorphic pyrite phenocrysts which most likely oxidized to goetite and washed away. Astute observers might have seen very small strain shadows preserved around the cubic grains in the form of fibrous quartz. This particular hand sample comes from the axial region of a tight fold. In the axis, the cleavage is perpendicular to bedding (which can be seen on one end of the sample. This causes the rock to break at 90° angles, creating a “pencil structure”.

1. (1 pt) What is rock?
: 1 point given for either shale, mudstone or slate.

2. (1 pt) What is missing from those cubic holes?
: 1 point for either pyrite or phenocrysts.

3. (1 pt) shape:
: 1 point for mentioning “pencil” or “fold axis”.

Succulent of the Week - Crassula argentea cv. gollum (??)

Some succulents are apparently easy to hybridize, and lots of strange freak plants are produced for the pet trade. When I bought this tube-wormy, translucent plant I had no idea what it was, and it doesn't seem to resemble any of the naturally occurring species very closely.

Dr. Internets tells me that this little guy will grow up to a small "tree succulent" with woody stems and clusters of finger-like leaves at the ends, looking remarkably like the whole plant looks now (e.g. this photo). Wonder how long that will take?

If I had known it was a cultivated hybrid instead of a "real plant" I think I wouldn't have bought it. Am I becoming a succulent snob? In spite of its decidedly non-deserty appearance, it seems to do just as well with long dry periods as my other pets.