Sunday, September 19, 2021

Comment: Dan is away, but thinking of you...

The parrotfish were plentiful... 

Diving with a few friends at the Salt Pier

... and the weather very fine on Bonaire this past week.  

But in my post that told you I was here, I presented two small mysteries about these next photos.  





And, as expected, the ever-prescient Remmij got the identification just right.  

The top fish is a Schoolmaster snapper (Lutjanus apodus) – yellow fins, medium size, the vertical bars are absent in older adults (see also the Wikipedia entry for L. apodus).  

In the second images, the blue/gold fish is Creole wrasse  (Clepticus parrae).  

It turns out that this is a hard identification problem--the Creole wrasse Wikipedia picture is not representative.  Check out this grid of images of the Creole wrasse to see the variations: 


 

Look at the images if you search for images of Clepticus parrae – it’s mostly blue fish.  But they change a lot over time.  The above image (mostly blue with a yellow tail) is common, but so are entirely blue fish. – or look at the variety of colors and patterns on the ReefGuide site.  This is common among reef fish—very different appearances at different parts of life.  An article from the University of the West Indies about the life of Creole wrasses points this out:  "During the initial phase the creole wrasse is purple/blue in colour, and upon reaching the terminal phase they appear purple. Larger individuals display a wash of yellow on the lower two thirds of the body..."  


To search for these fish, you can do a Search-by-Image IF you isolate a single fish in your search (it's tough to identify an entire school, en masse).  Here's me focusing in on just one fish in the big school... 


And it will, remarkably, give you a decent first result!  
  


Of course, you'd go on to double check this..  Yes?  

In my case, I've been diving long enough that I can recognized the general family of the fish: the top one is clearly some kind of snapper while the bottom one is clearly some kind of wrasse.  

General point:  Learning family (or classes) like this is incredibly useful.  When you're learning to identify something, make a bit of effort to understand what the natural categories are.  That will help you tremendously when searching for a specific instance.  

As we've discussed before, finding a fish identification key is an excellent move.  You'll learn these categories (such as "wrasse"  "snapper" "trunkfish" etc.), and you'll pick up lots of fine distinctions along the way.  

So I did a search for: 

     [ fish identification key Caribbean ] 

and while there are many online keys out there, I recognized the one at SpeciesIdentification.org as a familiar one.  

By using that key, I was able to focus in on the Creole wrasse and the Schoolmaster as the identity of the fish.  


I ALSO asked about the blue sponge in the background.  And Remmij is absolutely correct:  It's a Row pore rope sponge (Aplysina cauliformis).  I recognized it as a sponge, and did an image search for: 

     [ sponge Bonaire ] 

and quickly learned about Rope sponges.  A query modification to: 

     [ rope sponge Bonaire ] 

zeroed in quickly to the Row pore rope sponge.

Remmij - If you've got a moment, can you recount what you did to find this particular sponge?  (There are a lot of sponges out there! How did you do it??)  



Search on! 

Friday, September 17, 2021

SearchResearch Challenge (9/1/21): Floods, floods, and history?

 Floods come in all sizes...  



But this week we're interested in the biggest floods that have reshaped the land at large.  

What can we learn about such events?  Here's the Challenge from 2 weeks ago:


1. Can you find the 3 largest floods of all time?  What are they?  We're not counting life or property loss here, we're just interested in size--especially total water movement. Hint: they all have to do with geology rather than human-made causes.  

2. What causes these gigantic floods?  That is, how would such things occur?  What's the underlying root causes? 

3. Where are the biggest risks of giant floods today?  Sure, every dam in the world can cause flooding, but are there other places that might have a giant flood today?  Where?  And how bad are the risks?  


Like several of our SRS Regulars, I started with the simplest query: 

     [ largest floods of history ] 

The first result is a Wikipedia result, "List of deadliest floods," interesting, but not quite what I wanted.   

The next few results are all giant floods within the past few years, mostly historic, but again, not what I'm looking for.  The loss of life and property is tragic, but off-topic.  Even the largest historic floods (such as the 1931 floods in China, which flooded huge areas of China, killing somewhere between 400K and 4M people) aren't on the scale we seek.  

Fortunately, about 12 results down I found the USGS PDF "The World's Largest Floods Past and Present: Their causes and magnitudes."  

The USGS has a great reputation for being an authoritative source of geological (and in this case, hydrological) information.  This report covers the biggest of the biggest floods going back 2.5 million years, that is, it covers floods during the Quaternary Period, which goes from today back to 2.5M years ago.  

This chart summarizes the biggest floods of the Quaternary Period: 


When you read the report, you'll see that the biggest ones are due to ice-dam failures.  

The largest (by reasonable estimates) was the Kuray flood in Altair, Russia.  Near the end of the last glacial period, 12,000 to 15,000 years ago (late Pleistocene), glaciers coming down from the Altai mountains dammed the Chuya River.  This created a large glacial lake backing up into two large watershed basins. As the lake grew larger and deeper, the ice dam eventually failed, causing a catastrophic flood that spilled along the Katun River.  At peak flood, the Kuray (aka Altai Flood) is estimated to have spilled around 18M cubic meters / second.  (For contrast, Niagara Falls runs at 2800 cubic meters / second, 0.01% of the flood volume.)  

In North America, the largest Quaternary Period flood was the Missoula flood at 17M cubic meters/second.  It formed behind the Cordilleran Ice Sheet margin in the western US.  When the ice dam broke, it made giant floods along the margins of the Laurentide Ice Sheet in eastern and central North America.  These large ice-age floods involved tremendous volumes of water, enough that their rapid discharge into the oceans may have affected oceanic circulation, and even affected global climate.  Repeated failure of the ice dam released the backed-up glacial Lake Missoula, repeatedly causing dozens of catastrophic floods in eastern Washington state.  They can be seen in the geologic record as they removed tens of meters of pale loess from dark basalt substrate, forming scars along flowpaths visible from space.


But as I read that report, I found this intriguing sentence: 

"Geologic records also document tremendous marine floods into tectonically closed basins. The largest known example is the flooding of the Mediterranean Basin through a breach developed at the Straits of Gibraltar—an event now recognized to have caused the faunal upheaval used by early geologist Charles Lyell to divide the Miocene and Pliocene Epochs."

Really?  

A quick search for: 

     [ Mediterranean Basin flood ] 

led me to even LARGER floods!  

Why were they not included in this paper?  Because if you remember, the USGS report covers only the Quaternary Period.  That is, from today back to 2.5M years ago. 

Here's a chart for reference.  The USGS paper only covers the Quaternary (that is, the Holocene and the Pleistocene).  





Digging into some of the results of that search tell us that before 5.3M years ago, today's Mediterranean was a huge basin with hyper-salty water. (Ready all about the 
Messinian Salinity Crisis, which tells us that the Mediterranean Sea went into a cycle of partial or nearly complete drying-up throughout the latter part of the Messinian age, from 5.96 to 5.33 million years ago. The Salinity Crisis ended with the Zanclean flood, when the Atlantic reclaimed the basin by pouring through the Straits of Gibraltar.  

How big was that flood?  A paper in Earth Science Reviews (The Zanclean megaflood of the Mediterranean – Searching for independent evidence) tells us that there's a good deal of evidence for this megaflood, including 

"...Numerical model predictions show that sand deposits found at the Miocene/Pliocene (M/P) boundary in [several] sites... are consistent with suspension transport from the Strait of Gibraltar during a flooding event at a peak water discharge of around 1B cubic meters/second."  

That's astounding!  It's so remarkable that I (following our usual guidelines to double/triple check things that amaze you) searched for a few more articles on the Zanclean flood. 

This time I used the new terms I picked up in my reading megafloods  and outburst flood.  That led me to search for: 

     [ prehistory megaflood OR "outburst flood" Zanclean ] 

Which led me to a Nature article (Catastrophic flood of the Mediterranean after the Messinian salinity crisis) a Science Daily article (Evidence for a giant flood in the central Mediterranean Sea) and several others--all of which agree.  The refilling of the Mediterranean after the salinity crisis was quite probably the biggest flood of all time. 

Just for completeness, I also did a search for: 

    [ list of megafloods ] 

Which took me to the Wikipedia list List of Megafloods, which includes the Zanclean flood and a few others that I didn't know about.   (All of which were smaller than Zanclean.) 


What about risks of large-scale floods today? 

Using that speciality term, megaflood, I did a search for: 

     [ megaflood risk ] 

which led to a number of articles about the risk for large-scale floods in the US.  (The results will vary a bit depending on where you're located when you do the search.  If you're in Iceland, you'll get more localized results.  The same is true for other places.)  

The most worrisome article was one from Scientific American, California Megaflood: Lessons from a Forgotten Catastrophe which points out that while California is currently drought-stricken, it's not impossible for another 43-day storm (like the one that began in December 1861 that dropped 2 meters of rain) could put central and southern California underwater for up to six months.  We need water, just not that much water THAT quickly.  

SUMMARY:  

The largest known floods of the past 1.5M years had peak discharges of nearly 20 million cubic meters/second and were caused by breaches of glacial-age ice dams that blocked large midcontinent drainage systems. 

Most of the other largest documented floods resulted from breaches of other types of natural dams (such as landslide dams, ice dams of smaller glaciers, releases from caldera lakes, and ice-jam floods).  

Surprisingly, only 4 of the 27 largest documented floods were the result of meteorological conditions and atmospheric water sources.  But unsurprisingly, the biggest risk of contemporary megafloods is due to concentrated rainfall in increasingly urban areas, much as we have seen in recent flooding events in New Jersey (from Hurricane Ida), in Henan, China, and in Europe this past summer.  

But for the LARGEST floods of all time, we have to include the Zanclean Flood and the ice dam floods like the Kuray flood and Missoula floods that left dramatic marks on the geography of the area.  


SearchResearch Lessons 

There are 4 highlights from this week's Challenge:  

1.  Rapidly skip irrelevant results.  Several of these queries bring up amazing stories and remarkable events.  But stay focused on what you're seeking.  (If you want, take a note to come back later--but when you're working on a deadline, be sure to keep your eyes on the prize.)  

2. Remember the scope of your source material.  When were reading that great USGS paper about "largest floods," we had to remember that it only covered the Quaternary floods... and there were even bigger floods before that epoch.  Take note of the limits of what you read--you might be accidentally excluding information that is really what you want!  

3. Triple check your amazing discoveries.  This is general advice worth remembering.  Every time I found "the biggest X" or the "largest Y," I'd go look for at least 2 more citations that would confirm (or disagree!) with what I'd just found.  

4.  Use specialty terms you learn along the way (e.g., megaflood). Often when you start searching in an area that you don't know well, you'll pick up on specific terms that help you in subsequent searches.  "Megaflood" was a great search term--it's unusual enough to be very specific and incredibly useful.  Note these as you do your reading, and your searching will improve!   


Search on! 

Monday, September 13, 2021

Dan is away, but thinking of you...

 It's been a long, lovely week... 

Diving with a few friends at the Salt Pier

... while vacationing in Bonaire, the home to parrotfish (see our previous discussion of parrotfish in SRS) and many other wonderful things to investigate.  I'm sure some of them will be featured in future SRS posts.  

I'll try to post an answer to our previous SRS Challenge ("Biggest Floods") later this week, but don't be surprised if I'm a day or two late. 





If you find yourself needing a bit of an SRS fix, you might try to identify the fish above.  (Extra credit if you identify the creature (looks like branching fingers) that's behind the blue/yellow fish.)  

I'll be back above water soon! 


Carry on.. and, as always, Search on! 


Wednesday, September 1, 2021

SearchResearch Challenge (9/1/21): Floods, floods, and history?

 As you might have noticed, I'm fascinated by floods. 

Flooding in Texas, 2021.  P/C NSF


We've investigated floods before in this blog.  See SRS in 2016 when we asked "what's common between these floods?"  or this SRS from 2020 when we discussed flood and debris basins near Los Angeles.  

There are certainly a LOT of floods this year (Tennessee, Louisiana, North Carolina, Belgium, China, etc.) and perhaps that's why floods are on my mind this week.  

But, as always, I'm interested in even BIGGER floods that have reshaped the land at large.  

I've heard about such things:  Epic floods that created canyons and seas, changing the very shape of the countryside, but I don't know the details of when and where such floods have taken place.  Can you find out? 


So this week's Challenge is about really big floods... 


1. Can you find the 3 largest floods of all time?  What are they?  We're not counting life or property loss here, we're just interested in size--especially total water movement. Hint: they all have to do with geology rather than human-made causes.  

2. What causes these gigantic floods?  That is, how would such things occur?  What's the underlying root causes? 

3. Where are the biggest risks of giant floods today?  Sure, every dam in the world can cause flooding, but are there other places that might have a giant flood today?  Where?  And how bad are the risks?  


I love these kinds of SRS Challenges because they make me look for information in resources that I don't normally visit.  They make me think on time-scales and sizes that are much larger than myself.  I hope you enjoy these Challenges for the same reason.  I hope they pique your curiosity and inspire further research on your part.  

Speaking of "further research," my plan for the next two weeks is to visit Bonaire on a scuba diving trip with a few good friends.  I HOPE I'll be able to post an answer next week, but if I'm not able to do so, you'll know why.  Not to worry--I'll return shortly.  

With any luck, I'll come back with more SRS Challenges having to do with marine biology, cultural anthropology, or geopolitics.  In any case, I'll be indulging my curiosity with a bit of field investigation.  

Search on!