The 1964 Alaska Earthquake & Northern Acorn Barnacles - Why Knowing Lots And Integrating What You Know Is Useful

I'm reading Henry Fountain's The Great Quake:  How the Biggest Earthquake in North America Changed Our Understanding of the Planet.  It's for my October book club meeting.  We're actually discussing David McCullough's  The Johnstown Flood at our next meeting, but it wasn't in the library and Quake was.


The whole Quake book is about figuring things out - basically, how the field of geography was still resisting the idea of earthquakes being caused by shifting tectonic plates.  I took geography at UCLA in 1963 (a year before the Alaska earthquake), and I don't recall anything about plate tectonics in that class.  Fountain argues that what the learned from the Alaska earthquake moved the field to accept plate tectonics.

But I want to focus on a tiny part of the data collected after the earthquake.  Fountain focuses particularly on a field geologist with the US Geological Survey - George Plafker, who had done a lot of summer field work in Alaska.  The USGS sent him and Arthur Grantz and Reuben Kachadoorian to Anchorage immediately after the quake.  They did a lot of flying around, taking pictures, talking to folks, and generally documenting changes in the landscape immediately after the quake.  (I'd note the turned out a report on the earthquake on April 27, 1964, just one month after the quake.  I can't imagine too many government agencies pulling that off today.  It was a preliminary report with lots of qualifications, but still, it was out there.)

Pince William Sound Google Map 

He came back up again for the summer to study uplift and subsidence in Prince William Sound.  Fountain writes that so much of the land to be studied was on the water where things were easier The Don J. Miller -  at their disposal.  (Don Miller was an old mentor of Plafker who had drowned in Alaska.)
to see and measure.  He points out that Prince William Sound (about 100 miles from east to west - Cordova to Whittier) has about 4000 miles of coastline.  But they had an agency flat-bottomed motor barge -

"The Don J. Miller, Plafker realized, would make most of [the coastline] easy to reach.  And measuring the changes in elevation along it would be made easy by something else:  the barnacle line.

Plafker had first learned of the barnacle line during his two weeks in Alaska immediately following the quake and had talked to marine biologists then to better understand how barnacles fit into the environment of the Alaskan coast."

Newfoundland Rock Barnacles - *see note below

Barnacles had been used to measure uplift and subsidence after a previous earthquake, but Fountain says that Plafker and his crew perfected the technique.

"The concept was relatively simple.  Because northern acorn barnacles establish themselves at a certain spot on rocks and pilings - at or close to mean high water - they could be used as a reference point to measure both uplift and subsidence.  In an area where the land had risen up, the prequake barnacle line would now be higher than it was before, and out of the water.  After a few weeks the barnacles would have died, but their white- colored plates remained, firmly cemented to the rocks or wood.  For ears where the land had sunk, the barnacle line would now be underwater most or all of the time.  Either way, to determine the amount of elevation change, in most cases all that was needed  was to know the stage of the tide - which the US Coast and Geodetic Survey had been busy recalculating all over Alaska after the earthquake - and them measure from the waterline to the top of the barnacle line."

Fountain explains it's a little more complicated than that and gives details, then writes:

"Later in the summer the work became easier and Plafker found that often he didn't need to worry about the tides at all.  Late summer was when juvenile barnacles, which had hatched after the quake and developed, settled down for good - at the new, post-quake mean high-water line.  Then Plafker would have two barnacle lines - before and after - and determine the elevation change was simply a matter of measuring the distance between the two."

There were, Fountain points out, areas where there were no barnacles, such as where the rocks were exposed to strong waves.  But there was a type of seaweed - Focus distichus, or Rockweed - that offered a similar mark that could be used.


I'm writing about the norther acorn barnacle here because I think it's cool, the way that these scientists used knowledge in one field to assist them in this difficult task of measuring how much the land had risen or sunk due to the earthquake.   The more we know, or communicate with people who know other things, the more we are able to integrate that knowledge to know more.  I also have to think about Alexander von Humboldt, about whom I wrote not long ago, who had this incredible breadth of knowledge across different fields that enable him to see what most people couldn't.


*Newfoundland Nature calls this a 'northern bar 'acorn barnacles' AND '  balanus balanoides.  I found other pictures labeled 'northern acorn barnacle' but also called semibalanus balanoides.  The Effects of Land Level Changes on Intertidal Invertebrates, which references George Plafker's use of the barnacle line, his barnacles are identified as balanus balanoides.  Other northern acorn barnacle pictures I found were also labeled semibalanus balanoides. They also required permission to use.  But I'm sure these are very close, if not the exactly the same sort of barnacle. I was hoping to find some pictures of the barnacle line - I'm sure I have my own somewhere from pictures I took kayaking in Prince William Sound.  If I find one I'll add it.