#1:  Tremors

Look Mom, weird prehistoric underground monsters!

Geologic Sin Meter:  Graboid-Tastic

Geologically speaking, this classic goofball sci-fi flick is nearly devoid of sins, although there is a major biological question that is presented.  Though science is really not the focal point of the movie, geology plays a significant role.  Characters “hide” using rocks, the geology of the area is discussed as a means of escaping the monsters, the fossil record is discussed, and there is even quite a bit of geology lingo such as “pleistocene alluvium” and “precambrian”.  Many shots in the movie are of beautiful rock formations and the gorgeous basin and range topography of southern Nevada.  As a bonus, a large cliffed-out canyon is the means by which the last “Graboid” is dispatched of.  Geology!

Movie Background:

Welcome to Perfection Valley, Nevada.  Population: 14.  Then 13. Then 12.  Then 10.  Then some unfortunate road workers.  Val (Kevin Bacon) and Earl (Fred Ward) are local handymen trying to change their dead-end existences by leaving Perfection forever, but they are compelled to stay when the townsfolk begin to disappear under strange circumstances.  

Rhonda (Finn Carter) is a PhD candidate seismologist, studying the area with seismographs trying to get a beat on seismic activity.  Together, they discover and then outrun underground worm-monsters that devour everything in their path, and have to save the people of Perfection from a gruesome demise.

Geologic Background:

There are a few geologic angles to this movie.  The science of seismology, the geologic province in which these monsters are found, as well as paleontology and the fossil record.  

Seismology is officially defined by Webster’s as “the study of earthquakes and the propagation of seismic waves through the ground”.  These scientists are commonly referred to as geophysicists, and are somewhat loosely related to geologists who study physical rocks and their deposition.  

Seismologists or geophysicists are more interested in using seismic waves to infer subterranean geology, and their work is the basis on which our theories about the interior of the Earth (the mantle and core) are derived.  

They are also interested in monitoring seismic activity in the subsurface to make inferences and predictions about earthquakes and earthquakes hazards/risks.  Nearly all seismologists and/or geophysicists have geology backgrounds, but chose to do their graduate work in the more specialized field.

A seismograph (courtesy American Geophysical Union)

In the movie Rhonda LeBeck (Finn Carter) is a graduate student from MSU (?) as denoted by the initials on her seismic equipment.  Although it is unclear exactly what she is studying, she is using the seismographs to gather information about seismic activity in the area.  

A seismograph is a tool used by seismologists to gather information about energy and motion in the Earth, specifically during earthquake events.   They are very useful in determining the force and duration of seismic events, and play the role in this movie of alerting our heroes that a Graboid is near (Yay!).

The geological province in which the movie is set is known as the Basin and Range.  It extends west, south, and southwest from the Colorado Plateau, essentially from northern Arizona and New Mexico south well into Mexico, and west from Las Vegas to the Sierra Nevada.

Map showing the location and general extent of the Basin and Range province (courtesy earthscope.com)

The province is characterized quite literally by low basins in which sediment accumulates, and northwest-southeast trending mountain ranges that are bound by normal faults.  It is an area of extensional-type tectonics, meaning that the crust is being pulled apart or rifting.  

The prevailing theory for how the Basin and Range has come to be is related to the Laramide Orogeny that built the Rocky Mountains.  Long ago (80-55Ma), the Farallon tectonic plate subducted the North American plate, building the Rockies.  

A cartoon rendering of the subduction of the North American plate by the Farallon plate (courtesy usgs.com)

At some point between 5-15Ma, a piece of the Farallon plate snapped off, and is currently “floating” in the mantle under the modern-day Colorado Plateau as suggested by current geophysical research.  As a result of this “floating”, the western portion of the North American continent is “sliding” westward, creating this large area of extensional tectonics.  In fact, geologic research indicates that San Francisco, CA was once located near what is now Flagstaff, AZ prior to the extension taking place.

A timelapse rendering of the action of the Farallon, Pacific, North American, and other related tectonic plates to create the Colorado Plateau, Rocky Mountains, and Basin and Range province (courtesy usgs.com)

Paleontology and the fossil record also play a critical role, as it is one of the central question of this film, “where did these things come from?”  There is a debate amongst the three central characters as to the answer of this question, and one of the theories put forth is that they pre-date the fossil record.  

The fossil record goes back roughly 3.6 Billion years, beginning with an animal known as the Stromatolite, which essentially is algae.  Life on Earth existed as single-celled organisms for hundreds of millions of years until the “Cambrian Explosion”, wherein many vertebrate fossils begin to appear and there is a proliferation of diversity in life.  

From there life moved out of the seas and onto land, and evolved into humans and all the variation of creatures that we see today.  This is obviously an extremely simplistic and stunted version of this story, but we only have so much space here.

Where do Graboids fit into this story, you may ask?  Well, that answer is the main part of our Sin QnA.

Geologic Sin QnA:

Could an animal like this really go unnoticed for that long?

A Graboid in all its glory (courtesy pophorror.com)

Herein lies the main geologic, or more aptly biologic sin of this movie.  In terms of evolutionary biology and ecology, the existence of the Graboid is a near impossibility.  How could an animal this large and voracious have possibly gone undiscovered, or have even evolved?  Well friends, on both counts it almost certainly could not have.  

Strip away everything else for a moment, and it still seems highly unlikely.  Never mind that these animals have nothing to move their giant bodies but small spikes, and that they only exist just below the ground.  Never mind that to have evolved into this form would have taken tens, if not hundreds of millions of years and lots and lots of large food or an extremely efficient metabolism.  Never mind that, despite feeding on livestock and humans, nobody has ever seen them.  

Take all of that away, and what we still see is a creature that, in its current environment of the Perfection Valley, is all but locked in by hard-rock mountains on each side, large, sheer-cliffed canyons on the other side, and a serious lack of a reliable food source even if they did escape the valley.  The Mojave desert is a wild and inhospitable place, particularly for large predators like a Graboid.  Maybe the occasional Bighorn Sheep would do the trick?

Debating anything beyond simply the vacuum existence of these creatures is pointless, and the deeper you delve the more reason you find that, scientifically speaking, it is a near biological and evolutionary impossibility for these creatures to exist in this state, essentially crushing the main attraction of this movie.  Bummer, because it would be super cool to see a Graboid.  

However, it does still leave the possibility that they are extra-terrestrial.  But…..They could not have survived the impact of an asteroid that would have deposited them, nor do they seem capable of constructing and piloting their own ship.  Maybe they were placed here by more sophisticated aliens or even human beings?

The placement theory could be interesting, as it was suggested in the movie.  Val surmises that they are an invention of the Russians.  This suggestion, made during the waning years of the Cold War, is absolutely possible, maybe more so than any other legitimate suggestion.  I

t is possible that they were created in a Soviet genetic laboratory, deposited as babies in the remote areas of the Mojave Desert, and survived and grew as they fed on the local cuisine of coyotes, bighorns, the occasional lost hiker, and eventually the people of Perfection.  Was it the intention of the Soviets to have these animals infiltrate a large city like Las Vegas or Los Angeles and create mass panic and confusion, thereby giving the Soviets an opportunity to seize the moment and overtake our government?  Seems likely :).

Is the geologic terminology used correctly?

Yes.  A few geologic lingo drops are to be found, including a reference to “pleistocene alluvium” and “precambrian”, as well as discussions of topography, which is dictated by geology.  Pleistocene alluvium, or more simply referred to as “dirt” by Rhonda to her slack-jawed audience, is exactly what collects in the basins of the basin and range.  

Although is it more commonly referred to as Quaternary alluvium, this is still generally correct.  What is the difference?  The Pleistocene is an epoch (1.8Ma-10Ka) within the Quaternary era (1.8Ma-present), most precisely the epoch in which the last ice age occurred, ending roughly 10ka ago.  We are currently living in the Holocene, which has its beginnings when the ice melted and the glaciers retreated.

The groups using geology to their advantage (courtesy pop horror.com)

When someone is referring to Pleistocene alluvium, they are typically referring to sediment deposited by glaciers.  In the basin and range,  sediment is deposited in the basins by runoff from the mountains (ranges) following precipitation and mass movement events, and likely not from glaciers (even during the Ice Age).  In addition, it would be very difficult, if not impossible to absolutely date this alluvium to the pleistocene era, which is why we geologists generally refer to unconsolidated sediment moved by water as Qal (Quaternary alluvium) on geologic maps.

What possible purpose would a graduate student in seismology serve in this area?

Well, the same purpose that any student of science would serve anywhere:  To gather and record data that may be of use to major and groundbreaking scientific research.  We all want the glory, and a few of us find it out in the field.  More specifically, seismic research in the basin and range is important because it allows us to infer the location of active faults, which is useful in determining earthquake hazards.

Would the groups escape plan really have worked?

In short, yes.  The Graboids are very adept at moving through the unconsolidated sediment that fills the basins.  Heading for the mountains, and therefore the consolidated and lithified rocks such as granite and metamorphics such as gneiss that are typically found in mountains would have stopped the Graboids dead in their tracks.  Geology, as usual, will save the day.

Final Word:

This is one of my, and many of my colleagues’ (hence its #1 ranking) favorite movies.  Young Kevin Bacon trying to act cool to get the PhD-candidate seismologist, Fred Ward in a classically serious-yet-goofy role, country star Reba McEntire and Michael Gross as elephant gun-toting survivalists, and enormous, angry, hungry underground monsters that devour whole cars; could a movie possibly have more awesomeness?  The correct answer is no.

For a fun fact, the movie was filmed just west of Death Valley in the Owens Fault Zone, and not actually in Nevada.  However, these areas are quite similar geologically, topographically, and the scenery is very similar as well, so this is not so much of a sin as much as just the realities of Hollywood and its propensity to film in one place and call it another.

 Despite the over-arching assumption the movie makes that these monsters have escaped discovery for thousands of years and have no fossils because they pre-date the fossil record (or something else?), this movie is just simply so fantastically goofball entertainment that it really does not matter.  Watch it; laugh, cry, scream, and smile until your jowls hurt, I promise that they will.  

May The Goat be always with you

Going Guided

Hiking and exploring our National Parks, or any of our public lands, is a special experience.  Although it is possible to see these places yourself, hiring a guiding outfitter is a great idea.  For instance, guiding services provide logistical support, and plan everything for your best possible trip.  They provide a great safety net on the trail, and are trained in backcountry medicine. Above all, they provide a depth of knowledge of the region that turns a walk into a true adventure.

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