A few weeks ago, my best friend and I climbed aboard a boat and struck out for Duiker Island, a seal, seal pup, and seal poop covered collection of rocks tucked around the corner from The Sentinel Mountain in Hout Bay, Cape Town. Why would anyone endure the swells and smells for such an excursion? Aside from the staggering beauty of the Cape peninsula and the pleasure of watching seals in their natural habitat, we were here to go snorkelling with them!
For one blissful hour, we escaped reality to submerge ourselves in the moody greens and blues of the Atlantic Ocean, where prolific kelp forests swayed and swished in the swell and the playful seal pups were close enough to touch. Usually, I use my words to describe experiences. This time, we hired a Go Pro camera from the company who took us out – Animal Ocean – to document it all and so I present to you my first ever (shoddy) attempt at putting together a travel video!
It’s too bad that seawater is salty, because with a bit of sweet flavouring, everyone would have had access to unlimited slushy “Slurpee” a year ago, courtesy of Mother Nature!
Video Source: “Giant Frozen Waves Nantucket Beach” Uploaded by Galaxy 11
The United States spent much of February of last year in the frigid grips of a record-breaking icy winter. Yet, in addition to the usual suspects, which include deep snow and biting winds, the cold would seem to have even won over the briny seawater of the north Atlantic Ocean. This video shows a series of images of ocean waves breaking on the shores of Nantucket in New England (northeast USA), only, there seems to be something distinctly different about these waves!
The photographer, Jonathan Nimerfroh, is an avid surfing enthusiast and on a trip to the beach, he noticed something odd about the horizon. As it turns out, the temperatures are so low in the area the water has begun to freeze and so, what we are looking at are giant slushy waves! These icy waves have also been aptly called “Slurpee waves”
The maximum temperature on the day these pictures were taken was at a teeth-chattering -7 degrees celsius (17 degrees Fahrenheit).
What’s truly amazing about this is that salt is known to lower the freezing point of water to well below zero degrees celsius. This is precisely why we throw salt over our driveways to prevent them from icing up. The fact that even the salty seawater in northeast United States began to freeze is testament to the uncharacteristically cold winter they had last year.
It’s a killer club song by DVBBS & Borgeous and it’s coming to a Pacific neighbourhood near you to totally ruin your day.
Tsunamis are big waves… the result of a monumental displacement of water that usually takes place at depth somewhere on the ocean floor, although they can also be caused in large lakes and by seismic events occurring at or near the Earth’s surface. The result is a colossal series of waves that only the most baked of surfers would attempt to tackle. The damage is potentially staggering should these waves make landfall and they frequently do.
Makin’ Waves: A How To Guide
As it was mentioned, tsunamis are most often caused by events that have the energy to displace enough water to give the coastlines of the adjacent continents a salt-water enema. What kind of events might these be?
Earthquakes, the result of a sudden and violent wrenching of Earth’s foundations, can kick the water up and around its epicentre into violent protest.
Fat celebrities jumping off their gazillion dollar luxury yachts.
Landslides can send many tonnes of rock and debris crashing into water, generating large waves that can wipe out beaches, forests and any and all human habitation.
Iceberg calving does the same as landslides, except, instead of earth and rock, it sends mammoth-sized chunks of ice and snow (and perhaps the occasional cryogenically preserved mammoth) careening into the ocean.
Volcanic eruptions can do both: they can cause incredible landslides of debris into the ocean or a lake and they can cause tremors and earthquakes violent enough to generate tsunamis.
And then there are meteorite strikes that can cause the kind of giant waves portrayed in end-of-the-world movies The Day After Tomorrow and Deep Impact. Even the detonation of nuclear bombs (refer to the totes adorbs film Finding Nemo) can cause billions of litres of previously peaceful water to relocate to your previously peaceful neighbourhood.
Mother Nature Can Be A Real Jerk
Yes, she can. You see, tsunamis – natural disasters in their own right – are typically conceived by natural disasters. As if an earthquake wasn’t enough to rattle your nerves, here comes a solid wall of water and debris to thoroughly spoil your day. This makes them the coarse salt in the wound of the earthquake stricken city – as the Pacific coastline of Japan tragically experienced in March 2011 – and they add insult to injury to anyone who has managed to claw their way through one natural disaster only to encounter another.
Tsunami means “Harbour Wave” in Japanese and the etymology (“word origin” for the vocabulary handicapped) is brilliant…
Japanese fishermen would climb into their creaky little fishing boats and spend the day out on the swell catching fish as fishermen in fishing boats do. Without noticing anything unusual at all, they’d return to the harbour with their soon-to-be sushi only to find their entire village looking particularly soggy and sorry for itself. And so, tsunamis became known as “Harbour Waves” because they didn’t seem to happen anywhere else.
But, how had something as conspicuous as a giant wave escaped their notice? Surely, the wall of water that is a tsunami would have flung the fishermen and their creaky little fishing boats into an abyssal wave trough before crashing ashore?
The answer would be “not necessarily” and here’s why…
Tsunamis are ocean waves, which means that they travel in a waveform and are governed by the same physical parameters and laws. They have wavelength (λ), which is the distance between the trough and the crest of the wave (refer to graph below); and amplitude (a), the distance from the ocean’s resting point to top of the crest.
In addition to having a wavelength and amplitude, ocean waves travel at a certain speed (ν) and with a certain amount of energy (E). People who study physical oceanography make use of all kinds of fancy looking equations to calculate these various parameters given one thing or another. I used to be very well-versed in these equations, since I majored in ocean and atmospheric science back at university. Since those distant book-bound days, however, an abundance of beer, travel and floozies has done its damnedest to erase my memory of these equations and replace them with sweeter recollections. So, I won’t subject you or myself to any math. Rather, I will explain in concept how physical parameters such as energy and wave speed affect wave size, which is something you’re going to WANT to know if your day on the beach takes an unexpected turn for the disastrous.
Water may travel in waves on the open sea, but each wave is in turn composed of hoards of molecules. So while we see ocean waves as a surface oscillation (an up and then down motion of the water) beneath the surface, the composite water molecules are tracing quite different paths. Water molecules in a wave travel in great ellipses, or circles. The molecules closest to the water’s surface have the most fun on the merry-go-round, which you can see in the diagram below, while those at the bottom, nearest to the ocean floor are seriously considering asking for a refund.
When a wave is far out at sea where the ocean floor lies many thousands of metres away from the surface, these particle motions are hidden beneath the water and are felt at the surface as a swell. Regular ocean waves or “wind waves” with a garden-variety wavelength of 30 to 40 metres (100 to 130 ft.) are experienced as the kind of rolling up-down motion that can turn you green around the gills if you have a delicate constitution.
Tsunamis, on the other hand, have such a large wavelength that for hundreds of kilometres the water would almost seem to go still as you ride up the side of a very long, yet shallow swell, which belies the presence of the roiling monster passing beneath your very feet. Out at sea, thankfully, you’re none the wiser and also totally safe. On shore, however, things are about to get super soggy.
As a wave travels towards land, the sea bottom rises to meet the continental shelf and then the actual shore. The shallower water slows down or decreases the velocity of the incoming waves. What doesn’t change is the amount of energy the wave is carrying. Think about it: energy IS speed. The faster you run, the more energy you burn. By comparison, relinquishing your hung-over self to the sweet oblivion of your couch requires hardly any energy at all.
Unlike your body, however, waves travelling towards the shore may slow down as they breach shallower depths, but the amount of energy contained by their infinite composite particles remains the same. It’s like running a marathon even though you’re facedown in your couch. Oh look! A quarter!
What does this all mean? Well, if a wave isn’t spending all that energy on travelling fast and yet its energy remains the same when it slows down, where the hell does it all go?
The answer is UP!
So, as a wave approaches the shore, it slows down and compensates by increasing in height. It then becomes visible above the surface of the ocean as rolling, tumbling water… the kind that stringy haired, gnarly Californians like to surf. Wave shoaling essentially explains this process. It’s how those great undulating swells you experience out on the open ocean turn into breaking waves on the shore.
As tsunamis hit shallower water, the seafloor rears up to become dry land and the entire monstrous size of the wave is revealed. It’s owing to the vast wavelengths (and small amplitudes) of these giant waves that they go by completely unnoticed on the open ocean by those Japanese fishermen. All that they would have felt was a slight sea swell, which would be virtually indistinguishable from any of the other swells they had been sitting on all day long. However, the up-to-200km wavelength of the tsunami and its arrival in shallower waters results in the sudden and eerie recess of the sea – like an anomalous low tide – only to bring it crashing back in a surge of super “high tide” that’s so swift and violent, beach goers have only seconds to plan their exit strategies. If there are palm trees nearby, make sure you pick a sturdy one.
You might be there awhile.
Tsunami Statistics (Say That Three Times Fast)
The December 2004 Indian Ocean tsunami that famously struck a number of Thailand’s popular resort towns was generated by a 9.2 magnitude earthquake and killed more than 230,000 people in 14 countries bordering the ocean. Over two million people were negatively affected by this tsunami with the greatest number of deaths being recorded in Indonesia (165,708). The estimated cost of the damage done to countries from Indonesia, Thailand and Myanmar to Sri-Lanka, Kenya and Somalia was $15 billion according to the Disaster Prevention Organization.
The March 2011 Pacific Ocean tsunami that struck Tokyo, Japan, was caused by a 9.0 magnitude earthquake – the largest to have affected Japan on record. The tsunami that made landfall on the 11th of the month reached over 9 metres (30 ft.) in height and caused $300 billion worth of material damage. It also claimed the lives of 15,884 people, according to CNN.com, which is not hard to believe when you take a look at some of the spectacular images to have been published after this disaster.
Class Dismissed: Your Take-Home Message
Tsunamis are big waves caused by the voluminous displacement of water via earthquakes, meteor strikes, iceberg calving, nuclear explosion, landslides, volcanic eruptions and Kirstie Alley at the beach during the nadir of her yo-yo dieting. Tsunamis are one cataclysmic event born from another and for this reason, they are devastating and yet deceptive, because we only know about them when they make landfall.
Owing to their unpredictable nature, they are (surprise) hard to predict and not all tsunami warnings culminate in a tsunami. Likewise, there could be no warning at all and you could find your pacific island holiday rudely interrupted. As with all natural disasters, however, they serve as needed reminders that we are by no means the most powerful force at work on this planet, nor will we ever be.
Welcome back to this, the second instalment of our foray into the field of plate tectonics in which we seek to understand how the giant bumping and grinding shards of crust that make up the surface of our planet have helped to shape it, create it, destroy it and give Hollywood directors endless material for disaster movies. In Part 1, we began our journey with a look at convergent boundaries – where two tectonics plates come together causing a fender bender of such epic proportions that it has resulted in some of the highest (Himalayas) and deepest (Mariana’s Trench) topographical features on Earth.
We discussed the difference between continental collisions (where two continental plates crash into each other) and subduction zones (where one denser oceanic plate gets “pushed” underneath a lighter, crustier plate). Both are characterised by plates that are slowly, yet inexorably colliding into each other and both result in some totally awesome environmental features, such as soaring mountain ranges, plummeting ocean floors, city-shattering earthquakes and volcanoes with monstrous cases of indigestion.
In this week’s blog, we’ll take a look at the other boundary types and what kind of geological party one might expect to find there…
2. Divergent Boundaries: When Two Plates Pull Apart
At the opposite end of a plate’s convergent boundary, one tends to find a divergent boundary. Here, the prodigious convection currents in the Earth’s asthenosphere (the squishy onion layer beneath the crusty lithosphere) serve to wrench the two plates apart. This exposes the bubbly mess of searing molten rock beneath. For the same reason you want to sew your butt cheeks together when you have a really bad case of “Delhi Belly”, this runny mess of lithic indigestion explodes out from between the plates causing all sort of fun for the neighbouring wildlife.
There are typically two geological features one finds at divergent plate boundaries and just as was the case with tectonic convergence, the resultant landscape depends very much on whether the plates pulling apart make up the continents or the ocean floor.
When the separation occurs between two oceanic plates, as is the case with the African and South American plate (in the southern Atlantic basin) and the Eurasian and North American plates (in the northern Atlantic basin), you get a mid-oceanic ridge, which doesn’t really look like Ronn Moss posing in the exquisite turquoise waters of some tropic paradise. No, mid-oceanic ridges are a lot bigger, a lot more ripped and far more complex, although perhaps not as emotionally so… and definitely not as annoyingly successful with the ladies.
Two plates can’t get away with divorce without some serious repercussions. For one, the divergent motion of the plates releases a whole lot of pressure on the underlying asthenosphere. It subsequently melts in relief, releasing a surface-bound flood of molten rock known as magma, or at least until it actually reaches the Earth’s surface, at which point it becomes known as lava.
Don’t ask me why geologists have to make things so complicated.
This lava cools and solidifies upon contact with the atmosphere or, in the case of mid-ocean ridges, the overlying water, forming blocky solid structures of igneous rock. Over time, the release of magma from the divergent motion of the plates forms wave after wave of new ground in a process referred to as “seafloor spreading”. This all explains why the age of the rock closest to a plate boundary is younger than the rock as little as 100 metres away! Cool, huh?
Some of the attractions one might expect to see on a routine exploration of a mid-oceanic ridge include deep gorges and valleys and formidable submarine mountain ranges that are, in height, taller than Mount Everest. When you’re not “oohing” and “aahing” at the fantastic topography, you can “ugh” at the local wildlife.
This sexy sock-face with nipples for eyes is actually a Deep-sea Pompeii worm, which typically hangs out near the hydrothermal vent chimneys found along marine divergent boundaries. This large sea squishy enjoys black smokers, long walks along the trench and its ambient environment close to boiling point. Hydrothermal Vent Eelpout fish, Giant Tubeworm and the Hydrothermal Squat Lobster are more examples of wildlife that find boiling water totally amenable. In fact, there is a whole community of specialised critters that have become adapted to life in close proximity to blistering, incandescent volcanic vents.
When tectonic divergence occurs between two continental plates, rift valleys can form. East Africa provides us with a beautiful example of this in the shockingly named “East Africa Rift Valley.” I mean, how left field can you get? Here, the splitting apart of the Somalia and Arabian portion of the African plate has caused the ground to sink in a complex series of fault lines. The resultant synclines (fancy geology speak for “valley” or “dip”) can become filled with water, as is the case with Lake Malawi, Lake Tanganyika and Lake Victoria… some of the oldest, deepest and largest lakes in the world.
“Hold on,” you say. You’ve referred back to the map of the world’s major tectonic plates and there isn’t a plate boundary anywhere near East Africa.
“How observant you are!” I exclaim saccharinely…
The Africa plate is in the process of splitting into two, like a giant amoeba or your mother’s personality when she drinks too much gin. The plate to the east of the Rift Valley is the Somali Plate and the one to the west is the Nubian or Arabian Plate (check out the diagram below). These two crusty offspring are referred to as “protoplates” or “subplates”.
What other exciting attractions do rift valleys have to offer us other than very old, very large and very deep lakes? Seismic activity of course, which includes all manner of fire, brimstone, earthquakes and highly specialized organisms that have adapted to the heat and the strange chemical environment found around aquatic volcanic vents.
3. Transform Boundaries: Where Two Plates Rub Together
We’ve looked at convergent and divergent plate boundaries, but what happens along the peripheries of the plate if the “front” is having a head-on collision and the “back” is being torn asunder?
If your guess was a great idea for a blue film, I commend you on your filthy mind. However, “transform fault” was more along the lines of what I looking for.
Transform boundaries are characterised by two plates grinding past each other. Since jagged rock rarely slides easily past jagged rock, this fault line tends to be the source of much rocking and rolling in the Earth’s crust. Every now and then – which is painfully slowly in geological time – one plate gets snagged on the other and they are brought to a strained halt. The pressure mounts as the one plate tries in vain to move on, but is held back emotionally by the other, until, in a sudden Earth-shattering shudder, they become unsnagged, sending the plates shooting past each other.
This is precisely why transform faults are notorious for causing earthquakes. One of the best-known examples of such a boundary is California’s San Andreas Fault (image below), which is currently – as we speak – being torn asunder by the divergent motion of the North American and Pacific plate.
San Andreas fault is also testament to just how stupid humans can be… building a massive city on a fundamentally unstable Earth foundation is a disaster movie begging to be scripted and cast with slack-jawed hunky men and big-breasted, blue-eyed blondes. Although, if you are a film director and find yourself being inspired by this, please consider casting me as the clip-board wielding, surprisingly young, yet double PhD-educated science floozy! I may not have blonde hair, but you know what they say…
You can easily sleep with a blonde, but a brunette will keep you up all night long.
Mila Kunis is scientific evidence of this fact.
The disturbing reality about San Andreas fault is that it’s been 107 years since a major earthquake has occurred, which means that all these long years, the pressure between the plates has been building. Sure, there has been a smattering of decent earthquakes in between the 1906 San Francisco event and the present day – the most recent being the 6.0 magnitude Parkfield earthquake of 2004.
Don’t get me wrong, a 6.0 magnitude will leave your martini shaken and not stirred, but according to the latest Uniform California Earthquake Rupture Forecast (kind of like a weather forecast, but for earthquakes), California has a 99.7% chance of experiencing a larger than 6.7 magnitude earthquake in the next 30 years! I.e. you can bank on it.
It gets worse: the chance that this earthquake could achieve a magnitude of 7.5 or more is a frightening 46%. This may seem like a paltry percentage at first, but if your tandem buddy had to suddenly turned to you on a sky dive and tell you there was a 46% chance the parachute wouldn’t unfurl, you’d most definitely soil your undergarments. You can bank on that, too.
Could the next “Big One” finally send San Francisco into sliding into the sea? Is “Frisco” about to become the next city of Atlanta?
Who can say? Only time… and the underlying tectonic plates. Not Enya.
Class Dismissed: Your Take-Home Message
Plate tectonics play an incredible large-scale role in shaping the surface of our planet. Of course there is a myriad of smaller scale (both spatially and temporally speaking) factors that mould the mountains you climb over, the oceans you swim across and the valleys you… bungee jump across?… to be with the one you love.
But, plate tectonics are the daddy of global scale change and transformation.
I met Superman through WordPress blogging. He found my humble blog and decided that he liked it enough to pester me with comments. Those comments turned out to funny and clever enough for us to establish a rapport. Before I knew it, we became Facebook friends. With the name “Christopher Reeves” how could I not?
In an effort to coax me out of my hiatus – which I’ve had to take because I’m studying an online course – he has written this exceptional blog post on the literal awesomeness of the oceans. I loved every word of it and I now reblog it so that all of you can enjoy it. I am tickled pink to learn that my absence is noted by my readers (or at least one of them)… and that Superman took the time to write this brilliant and humorous article, which applies the overarching philosophy of Why? Because Science so very well.
That philosophy is: if you make people laugh about science, they’ll understand it.
Mars blows. With so much recent hype and excitement about popping a rover on over to our rusty neighbor, we seem to be overlooking a couple of important points. First, Mars is crappy. It’s cold; the air is, well, not air; and most importantly, there are no attractive scientists actually on Mars. Sure, there are the massively important technologies that we have developed as a byproduct of space exploration to get excited about. Space program spin-offs have given us LEDs, temper foam, grooves in the road, and freeze-dried food. OK, that last part sounded really exciting before I read it out loud. Anyhoo, Mars exploration could provide a mess of dimly lit, red-desert landscape photos for computer desktop backgrounds. It may divulge powerful revelations about our place in the universe. It might even give us evidence of life on other planets, which would be awesome because, well, ALIENS! But…