Saturday, August 29, 2015

In With The Rains, Out With The Flames

Friday, August 28, 2015
11:36 pm

Most of our wildfires are actually started by lightning, but that doesn't mean you can have a tannerite party during a red flag warning.,

Hey everybody! I’m finally back from summer camp, and while I had an amazing time there, I am very excited to sleep in my own bed, practice lots of saxophone, get a job (hopefully related to meteorology), and, of course, get back to writing weather blogs. I came back in the nick of time, as we’ve got a lot to talk about today.

As I'm sure you have no doubt figured out by now, this summer has been one of the worst fire seasons in Washington's history. Many news stations said that the Okanogan Complex Fire by Omak was the largest in the state's history, but this is not true, as the many fires here have not merged into a single large fire. That title is reserved for the Carlton Complex Fire of 2014 (wow, we really are getting burnt up, aren't we?). I attached a couple amazing shots below of the Wolverine Creek Fire, a fire that has been burning since June 29 and has now burned over 50,000 acres. These pictures are from the USDA (United States Department of Agriculture) Flickr page.



And here is a map of all the fires occurring over Washington and Oregon. It looks like all of Northeast Washington is on fire!

Credit: Northwest Interagency Control Center

Now, let's take a look at our mega-summer-storm. I can't ever remember seeing a storm this strong this early in the season. Even if it were November, this would still be a sizable storm for our region. But August? Good golly.

At 4 am, the storm was off our coast and travelling to the NNE. This is a perfect track for regionwide high winds... and it is the same path that our storm last December. I have a blog on that December storm here and you should all read it because it has an intense video of me in the storm. It's the same general track as the November 13, 1981 windstorm, the December 12, 1995 windstorm, and yes, the infamous Columbus Day windstorm of 1962.

Take a look at the nice, tight bent-back occlusion in the image below. The low center is right in the middle of that spiral.

Image valid 4 am PDT: UW Infrared Satellite

Image valid 4 am PDT: UW Radar

As the morning went on, the low moved further and further north and kept its intensity. One of the great things about our new coastal radar is that you can sometimes see the low centers of these types of storms as they swing on by, and you can clearly see the center with this storm less than 100 miles off the mouth of the Columbia River.

Image valid 6:30 am PDT: NWS NW Water Vapor Loop


Image valid 6:30 am PDT: UW Radar

At 9:30, the storm is moving on inland, and right now (10:56), it is crossing the Olympic Peninsula just to the south of Cape Flattery.

Image valid 9:30 am PDT: NWS NW Water Vapor Loop

Image valid 9:30 am PDT: UW Radar

Winds are reaching their peak now and will remain pretty strong until around 1 or so. After that, they will die down, but things will still remain pretty blustery around here. We have a high wind warning up (when was the last time Seattle had one of those in August?), but given the forecast wind speeds (40-50 mph gusts), a wind advisory would be more appropriate. We just have the warning since we are in the summer and weather like this is practically unheard of. I mean, take a look at all the weather warnings over our area. I've never seen anything like that in the summer.



Rainfall from this particular storm will total around 0.5 to 1.5 inches in the lowlands, with several inches in the mountains, especially the North Cascades, putting an end to any fires there. Though the majority of the rain will not make it over to Eastern Washington, some rain will fall, and this, coupled with high humidity, will be a tremendous help for firefighters fighting the wildfires in NE Washington. They will have to battle with strong winds though.

Valid 05:00 am PDT, Tue 01 Sep 2015 - 72hr Fcst: Retrived from UW mm5rt modeling website

The rest of the week looks showery, but as far as major storms go, I don't see anything in the near future.

Charlie

Wednesday, August 12, 2015

Heavy Rains Friday

Wednesday, August 12, 2015
10:18 pm

Hello everybody! I have a day off from my counselor duties at Hidden Valley Camp so I thought I'd go ahead and write a blog about the upcoming rains later this week. We could get dumped on Friday, but there's still a lot of uncertainty. 

The weather down here sure was interesting though. I heard some thunder up at camp, and although I missed it, I heard through the grapevine that an intense thunderstorm passed right over Seattle. Today, Sea-Tac got more rain in 24 minutes than the previous 71 days combined. Also, Iwakuma tossed a no-hitter. I gotta say... today was a good day. Too bad it's cloudy for the Perseids meteor shower tonight, but hey, you can't get too greedy. 

Anyway, let's take a look at what we may be dealing with later this week. I get back to camp Thursday afternoon, and everything we do out there is in the great outdoors (including sleeping and eating), so even though I absolutely love the rain, it definitely puts a damper on activities. Me and my tent group of six 12-year-old boys are hiking Mt. Pilchuck on Friday, so I'm definitely interested to see what hiking in the rain with these kids will be like. By the way, the hike is only 5.4 miles roundtrip, but features 2,300 feet of elevation gain. I'm super excited, rain or shine.

Since I'm talking about Friday, I might as well give a brief talk about the weather we can expect Thursday. The newest models from the UW don't show much precipitation at all, but there will be a significant amount of CAPE (Convective Available Potential Energy) over the area in the afternoon, so some thunderstorms may develop. CAPE is defined as the amount of energy a parcel of air would have if it rose until it could no longer rise (i.e. it becomes colder and thus denser than the surrounding air). The more CAPE there is, the more unstable the atmosphere is, and the faster parcels rise. Because of this, high CAPE is an important ingredient for convection, but just because there is high CAPE does not mean there will be convection. There are many other factors that can inhibit convection... strong low-level inversions, high pressure systems, low vertical velocities of air parcels in the lower atmosphere to initialize convection... I could go on. There are plenty others. 

Valid 05:00 pm PDT, Thu 13 Aug 2015 - 24hr Fcst: Retrieved from UW Pacific Northwest Environmental Forecasts and Observations Modeling Page

Anyway, let's move onto Friday. I'm only going to give a brief overview, because the details are pretty murky for reasons I will explain shortly.

The rains are predicted to start heading into the area Friday morning.

Valid 08:00 am PDT, Fri 14 Aug 2015 - 39hr Fcst: Retrieved from UW Pacific Northwest Environmental Forecasts and Observations Modeling Page
A blob of rain will form south of the Olympics (at least in this model run)...


Valid 11:00 am PDT, Fri 14 Aug 2015 - 42hr Fcst: Retrieved from UW Pacific Northwest Environmental Forecasts and Observations Modeling Page

... and this blob will intensify and move eastward as the day progresses.


Valid 05:00 pm PDT, Fri 14 Aug 2015 - 48hr Fcst: Retrieved from UW Pacific Northwest Environmental Forecasts and Observations Modeling Page

This model run gives around an inch of rain to Mt. Pilchuck on Friday. This morning's run gave two. We'll see what tomorrow morning's run gives. All this variance in precipitation is due to a cut-off-low off the Northern California Coast. Since cut-off lows are not connected to the jet stream, they are rather erratic and hard to forecast. This cut-off low is responsible for Friday's uncertain forecast. There is an old weather saying: "cut-off low, weatherman's woe." That saying definitely holds true right now!

Right now, rain seems like a pretty good bet for Friday, but where and how much is up in the air. If the models are correct however, some places could see pretty heavy amounts, especially places north of Everett. But regardless of how much it rains, I'm prepared to have an awesome time climbing Mt. Pilchuck on Friday. 

Thanks for reading!
Charlie

Saturday, July 11, 2015

Why Such a Hot Summer?

Saturday, July 11, 2015
5:04 pm

Check them out! http://www.hvc-wa.com/

Hello everybody! I've been living in the woods for the past 3+ weeks up near Granite Falls, Washington, and there ain't no WIFI in the woods, so that's why the blogs have temporarily ceased. But right now, I am just relaxing at home, as I have a day off before I head back up to Hidden Valley Camp tomorrow. There are three camp "sessions"... the first one ended Friday afternoon, and the second one starts Sunday afternoon and ends in early August. For 1st session, I was a group counselor for a bunch of rowdy but lovable 10-year-olds, and 2nd session I will be taking care of 13-14 year-olds. I learned a ton during 1st session and had a great time, and I hope to have an even better time 2nd session. 

Anyway, let's talk about weather. It has been extremely dry and hot. Campfires are a big part of HVC, but we haven't been able to have them in many areas because of how hot and dry it is. I'm not getting my tan on this summer, but I am definitely getting my "dust" on, and when I go to take a shower at night, you can see a clear color change on either side of my sock, with lighter color below and darker above. The darker hues are not due to sun exposure. It is unbelievably dusty up there right now.

Why has this been happening? Well, there are two main reasons. The primary reason is that we have had a massive ridge of high pressure over our area. As my TV meteorologist friend Matthew Leach says, “high means dry”, and it also equals warm, as high pressure is associated with sinking air, and as a given parcel of this air sinks, it compresses and increases in temperature (note: because the temperature of this sinking air parcel increases but its volume decreases, the total amount of heat in the sinking air parcel remains unchanged). This process is known as adiabatic warming.

To illustrate how prominent this ridge has been, let's take a look at the 500 mb level heights from July 2nd. Sea-Tac had a high of 93 on this day (they had a high of 92 the previous day and had highs above 90 the next three days, tying the record for the most consecutive 90+ days (I believe it was set back in the early 80s)).  There is a huge ridge over the entire Intermountain West and Pacific Northwest.  

Valid 05:00 pm PDT, Thu 02 Jul 2015. Retrieved from UW mm5rt modeling site.

The secondary effect that contributes to our warmth is a large mass of unusually warm water off our coast. When we have onshore flow, the Pacific moderates our climate substantially, but if the air coming off the Pacific is passing over warmer-than-normal water, it will not cool off as much before it gets here, and we will see warmer conditions than one would expect without this warm water. As you can see, this warm water in the NE Pacific is quite expansive. This big mass of warm water appeared during last summer as well, and last summer was super warm, so when you consider that this summer is off to an even warmer start, it is not surprising to see the warm water reappear. Nick Bond, who is the state climatologist and a UW professor (I took a class from him and he is truly a first-class teacher and human being) casually named this big area of warm water "The Blob" last summer, and the name stuck. The Blob is back, and it is making us even warmer. The Blob tends to form under calm conditions where there are persistent ridges of high pressure that prevent warm surface water from mixing with cooler water from the depths below, and boy oh boy have we had our share of persistent ridges over the past couple weeks.

Retrieved from IRI Global SST Maproom

Was this predicted? You betcha! Look what NOAA's CFS model predicted earlier this spring. I couldn't find past CFSv2 simulations so I found this from Cliff Mass' blog post "Drought Misinformation," which I highly suggest you read. Contrary to popular belief, the Pacific Northwest didn't experience a precipitation drought this past winter. However, we are off to a hot and dry start to summer, so things could get worse for us if we don't cool off or get some rainfall.


Finally, the Pacific Northwest has been the hottest place (compared to normal) in the U.S. over the past month. Eastern Washington has been 6-7 degrees above normal. I remember reading the paper one morning late June and seeing the temperature forecast for the day. Walla Walla: 108. Riyadh, Baghdad, and Cairo: 105.

CPC Temperature Analysis

Thankfully, things have cooled off, and we will see some light shower tonight and tomorrow. It won't be long before the sun gives any remaining showers on Monday the boot, giving us mostly sunny skies and highs in the upper 70s for Tuesday-Thursday. There's a chance of more (gasp!) showers on Friday and Saturday, so the mega-heat looks to be gone for now. Thank goodness.

Thanks for reading! I'll update as often as possible.
Charlie

Monday, June 1, 2015

The Nepal Earthquake Part 2: Earthquake Types

Tuesday, May 26, 2015
6:38 pm

Comparison photographs taken from the same location on 4th Avenue near the intersection with C Street and looking west. Red arrows point to the west wall of the Army Navy store in both images. (Top photograph [1964] from U.S. Geological Survey Photographic Library, ID aeq00045; bottom photograph [2013] taken by R.G. McGimsey, U.S. Geological Survey, 2013.)

On Good Friday, Mary 27, 1964, Southeast Alaska was rattled by a 9.2 magnitude earthquake with a hypocenter some 15 miles below Prince William Sound. The damage throughout the region was simply astounding. 4th Avenue in Anchorage was absolutely destroyed by the quake, but a couple buildings on the south side of the street remained standing. Among them was Big Ray's Army-Navy Store (distinguished by the red arrow). My grandpa co-founded this store and my uncle and his family still run it today! Pretty cool, huh?

There are four general categories of earthquakes - tectonic, volcanic, explosion, and collapse. Tectonic earthquakes are associated with plates, volcanic earthquakes are associated with magma moving up from the mantle to the surface and causing earthquakes as it does so., explosion earthquakes are formed by, well, explosions, and collapse earthquakes are formed when something (say, an underground cave) collapses and makes a small earthquake The massive landslide that took off the north face of Mt. St. Helens was triggered by a volcanic earthquake The world had a lot explosion earthquakes during the 50s and 60s when atomic bombs were being tested, especially those underground. I'll stick to tectonic earthquakes here, since they are the largest and most destructive ones.

In the previous blog post, I talked about the three plate boundaries: convergent (and the three subtypes: oceanic-oceanic, continental-oceanic, and continental-continental), divergent, and transform. Not all tectonic earthquakes occur on fault zones, but the vast majority do. As the pictures below show, most of the earthquakes are centered across convergent, divergent, or transform plate boundaries. These "interplate" earthquakes contrast with "intraplate" earthquakes, which occur in the interior of plates and are relatively rare. The concentrated zone of earthquakes in East Africa is due to the East African Rift, which is a divergent boundary but is not illustrated in the diagram of the world's plates below. Additionally, a significant number of earthquakes are centered on "hot spots," which are locations of volcanic activity not affiliated with plate tectonics (Hawaii and Yellowstone are two examples of hot spots in the United States).

Credit: NASA.

The tectonic plates of the world. Credit: USGS.

These plate boundaries are manifested as faults, which are discontinuities or fractures in a volume of rock due to different plate movements that stretch, shear, or compress that rock. Not every single fault is a plate boundary, but all plate boundaries are faults, and it is these faults that are responsible for earthquakes. There are three main types of faults: normal, reverse, and strike-slip, and they each create different types of earthquakes. As you will see, these fault structures are very similar to the plate boundary structures I talked about in my previous post.

Normal Fault:

Anatomy of a normal and reverse fault. Retrieved from Wikipedia.

Normal fault. Retrieved from mamontoff.org

Normal faults occur when two masses are being pulled apart and one slides down the other. This is analogous to the divergent plate boundaries that form mid-ocean ridges. Earthquakes with these types of faults can be frequent, but they are weaker than the earthquakes caused by reverse or strike-slip faults because the diverging motion prevents large amounts of stress from building up.

Reverse Fault:


A reverse fault. Retrieved from San Dieguito Union High School District page on Faults

Reverse faults occur when two masses converge and one subducts under the other. These are analogous to the oceanic-oceanic, continental-oceanic, and continental-continental plate boundaries talked about in the last post, but remember, not all faults are plate boundaries. Extremely long reverse faults at subduction zones between plates can cause the largest earthquakes in the world due to the enormous stress that builds up as one plate is "thrust" under the other. Earthquakes occur when this stress is released. The largest of these earthquakes are called megathrust earthquakes. The one in Alaska in 1964 was a megathrust earthquake, and two more recent events were the 2004 Indian Ocean earthquake and tsunami and the 2011 Japan earthquake and tsunami. These megathrust earthquakes often cause tsunamis because subduction zones are generally located underwater, and these tsunamis can impact areas thousands of miles away from the epicenter of the earthquake. The marinas in Crescent City, California were heavily damaged from the Japan tsunami due to local bathymetry enhancing the effects of the tsunami. Most of the West Coast of the U.S. escaped unscathed though.

A reverse fault in the Grands Causses near Bédarieux, France. The right side moves up while the left side moves down. Retrieved from Wikipedia.

Strike-Slip Fault:

Anatomy of a normal and reverse fault. Retrieved from Wikipedia.

Strike slip faults are faults where masses of rock slide laterally past each other. The transform fault talked about in the previous blog is a special type of strike-slip fault in that the fault separates two continents. Fast moving strike-slip faults can cause frequent earthquakes, and the earthquakes that do occur are often very shallow and can therefore be extremely intense. The great San Francisco Earthquake of 1906 not only had a moment magnitude of 7.8 but occurred at a depth of 5 miles, and as a result, 80% of San Francisco was destroyed, with much of the damage due to fires throughout the city initiated by the earthquake that roared on for several days. This earthquake occurred along the most famous transform/strike-slip fault in the world, the San Andreas Fault.

San Francisco on fire in 1906. Credit: Library of Congress.

The San Andreas Fault along the Carrizo Plain. Credit: USGS.
__________________________________________________

In case you were sleeping too easily at night, Seattle lies directly under a reverse fault called the "Seattle Fault." This fault last shook approximately 1,100 years ago and delivered an earthquake having a moment magnitude of at least 7. While the Cascadia subduction zone off our coast can deliver much larger earthquakes (magnitude 9 or greater), the fact that this fault is right under our city makes it a far more dangerous fault for us. 

An approximate location of the Seattle Fault as looking from the west side of Puget Sound. Retrieved from Wikipedia

Reverse fault structures near Vasa Park. Retrieved from 2005 Seattle Fault Earthquake Scenario Conference

Predicted intensity of Seattle Fault earthquake throughout region. Retrieved from 2005 Seattle Fault Earthquake Scenario Conference

Everybody always talks about "the big one" waiting for us off the coast, but "the big one" is actually right below our feet!

Thanks for reading!

Charlie

Thursday, May 21, 2015

The Nepal Earthquake Part 1: Plate Tectonics

May 7, 2015
12:28 pm

I still remember the Nisqually Earthquake of 2001. Ironically enough, we had just finished an "earthquake drill" when our second-grade teacher shouted "Earthquake! For real!" We all immediately bolted under our desks, not necessarily because we were concerned about falling debris, but because we just liked bolting under desks. You could say it was a guilty pleasure of ours, I guess.

Many of those who have not been in an earthquake or who have not studied them equate them to the shaking and rattling of the Earth, but when I was under my desk, the movement seemed more akin to organized waves propagating throughout the room. When an earthquake occurs, it sends seismic waves from its hypocenter that travel thousands of miles per hour through the ground, so I have a feeling I was sensing the motion of these waves. It was actually pretty fun... I clearly remember having this vision of being in a boat on the water navigating through heavy seas, and these 'seas' were the seismic waves. Nothing was being damaged or falling down... it was just a little 15 second roller-coaster ride. Afterwards, we resumed school as if nothing had happened. The only place in Seattle that had sustained significant damage was Pioneer Square, which has old buildings that are not built to the same engineering standards as the other, more modern buildings in our area.

The Nisqually Earthquake may have been fun for 8-year-old Charlie, but the Nepal earthquake is horrible for everybody. There have been a number of severe earthquakes that the world has experienced over the past decade (Indonesia, Haiti, and Japan are just a few that come to mind), and the Nepal earthquake is right up there with them. Although it did not have the destructive tsunami that the earthquakes in Indonesia and Japan had, the damage that it has caused is simply unbelievable. Whole villages have been turned to rubble. Langtang Village, a small settlement of 435 people in the Langtang Valley north of Kathmandu, was buried under a landslide that, according to evewitness reports, was 2-3 kilometers wide and 100 meters deep. Seeing some of the destruction through pictures online makes me very sad, and I can't imagine how the friends and families of those affected must be feeling right now. A girl I grew up with and her friend are still missing from the quake and are presumed to have died (I wrote a blog post about it here), and the earthquake has directly impacted my community in a way I never thought it would.

I've always been not only a weather buff but an earth science buff in general, and that extends to geology. I think we can all agree that the Nepal Earthquake is terrible and we wish it never happened. But earthquakes themselves do not have any regard for life or property; they are just a natural consequence of plate tectonics. In that aspect, I think the Nepal Earthquake is a fascinating geological event, and that's what I'd like to blog about here since you hear so much about the death and destruction caused by the earthquake in the media. I hope you can join me in taking an interest in the geological nature of the earthquake and the processes that led to it.

This will be a three-part blog; the first part will explain some of the basics of plate tectonics, the second will explain the basics of earthquakes, and the third will look specifically at the earthquake in Nepal and how it compares to some recent earthquakes around the world.
____________________________________________________________________

Mt. Everest from Gokyo Ri, November 5, 2012. Retrieved from Wikimedia Commons.

In order to understand the Nepal earthquake, we first have to understand the geology of the Himalayas. The Himalayas are the world's tallest mountain range; out of the world's 10 tallest mountains, 9 reside in the Himalayas. The Himalayas are so tall for a variety of reasons, and not all of them are related to plate tectonics. They are young and located at low latitudes, and as such, they have not been heavily eroded by glaciers. The dominant reason why they are so tall, however, is due to the type of plate boundary that forms them... a continental-continental convergent boundary.

There are two general types of plates: oceanic plates and continental plates. Oceanic plates are thinner, denser, and comprised of basalt. Continental plates are thicker, less dense, and are mainly composed of granite. When one of these plates hits another plate, the less dense plate generally goes under the more dense plate. The characteristics of all plates are not the same, so some oceanic plates are denser than others, and the same is true for continental plates. There are many types of earthquakes, but the largest and most destructive ones are generally caused due to different plates smashing into each other. There are three kinds of these "convergent plate boundaries:" oceanic/oceanic, continental/oceanic, and continental/continental, so let's take a brief look at each of them and how they differ from each other.

The Aleutian Island chain is a great example of a convergent oceanic/oceanic plate boundary. The Pacific Plate is being subducted under the North American plate, creating a beautiful arc of volcanic islands and a deep ocean trench in the process. Note that the plates themselves are NOT the oceanic/continental crust; they are subdivisions of the lithosphere, which is the crust and the upper, rocky portion of the mantle. The movement of these plates is driven by convection currents on the asthenosphere, which, while still solid, is more viscous and deformable, and is liquid at certain locations, like mid-ocean ridges (more about those later).

Oceanic/oceanic convergent plate boundary. Retrieved from USGS.

Map of the Aleutian Trench and Islands. Retrieved from Wikipedia Page on Aleutian Trench.

The continental/oceanic convergent plate boundary is the one that we see along the West Coast of not only North America but South America as well. Our Cascades were formed by this plate boundary, and we will certainly have an extremely powerful earthquake within the next several hundred years, likely on par with the Japan earthquake back in 2011, and perhaps even stronger. The Andes are a textbook example of this type of plate boundary, as they have an extremely deep trench and very high (over 20,000 feet!) mountains in close proximity to each other. They have the strongest earthquakes in the world; the 1960 Nazca Earthquake was a 9.5 magnitude earthquake, which is approximately 800 times more powerful than our relatively puny Nisqually earthquake in 2001 (remember, earthquakes are measured on a logarithmic scale). These cataclysmic earthquakes are not just limited to continental-oceanic plate boundaries though, they occur at oceanic-oceanic convergent plate boundaries too. A 7.9 earthquake actually just struck the Aleutian Islands less than a year ago.

Continental/oceanic convergent plate boundary. Retrieved from USGS.

Continental-continental convergent boundaries create very high mountain regions for two reasons: no subduction takes place because the plates are too buoyant, and the plates have much more mass and are far thicker than oceanic plates. This leads to extremely high mountain ranges like the Himalayas of Nepal/Tibet and the Karakorum of Pakistan. These boundaries often create a massive plateau behind the main mountain range due to rock being pushed upwards instead of subducted. The Tibetan Plateau, which is five times the size of France and, on average, taller than Mt. Rainier, is a textbook example. These boundaries do not tend to have volcanoes and "megathrust" earthquakes (earthquakes approaching a magnitude of 9.0 or greater), but as we have seen in Nepal, they can still generate extremely powerful quakes.



Continental/continental convergent plate boundary. Retrieved from USGS.

These convergent boundaries are responsible for creating most of our mountain ranges. It makes sense intuitively; if you have a plate subducting underneath another, it's going to push that other plate up, and in the case of a continental-continental plate boundary, when subduction is not an option, the ground has nowhere to go but up!

As well as I'm discussing plate boundaries, I might as well briefly touch on the other two, divergent and transform, as earthquakes occur on all plate boundaries, not just convergent ones. Divergent plate boundaries arise when hot masses of the asthenosphere rise and burst through the lithosphere. This mass then cools, creating a new basalt crust and lithosphere. This formation of new lithosphere pushes each plate away from each other, causing them to diverge; hence the name divergent plate boundary.

Divergent plate boundary. Retrieved from USGS.


Ironically enough, divergent boundaries can create mountain ranges as well due to the magma rising through the lithosphere and cooling, forming a range. However, most of these ranges are underwater, because when plates diverge, seawater inevitably flows in after the rift between them has gotten large enough that seawater can flow through. Ever notice how the east coast of South America and west coast of Africa look like they fit with each other? Well, it is widely accepted that they were once connected in Pangea, which was a "supercontinent" composed of all the current continents, and that they began to break up 180 million years ago. In the middle of the Atlantic between these continents is the Mid-Atlantic Ridge. The Mid-Atlantic ridge is only one of many; the ocean is filled with these ridges.


Not all divergent plate boundaries occur underwater though. The East African Rift is a divergent boundary along equatorial Eastern Africa from Ethiopia to Malawi. There are several very deep lakes and stunning volcanoes in this area, including one that's becoming famous for its stark decrease in snow coverage (note: it's not due to global warming, it's due to deforestation).

Kilimanjaro's retreating glaciers. Credit: Penn State Department of Meteorology

Transform boundaries neither converge nor diverge; they slide right past each other. They differ from convergent and divergent boundaries in they are conservative plate boundaries, meaning lithosphere is neither created (divergent plate boundary) or destroyed (subduction zones). When plates are subducted or created, they are generally not done so in a uniform fashion, and rather have many individual transform faults connecting the overall subducting or diverging structure of the plate boundary itself. While they are most common around mid-ocean ridges, the most destructive ones occur near subduction zones on land. The San Andreas Fault in California is one of the most famous transform faults in the world, and is responsible for delivering many catastrophic earthquakes to the sunshine state.

The San Andreas Fault, an example of a transform boundary. Retrieved from USGS.

The San Andreas Fault has a striking structure and is something I would like to see in real life. Take a look at this photo below!

Aerial photo of the San Andreas Fault in the Carrizo Plain. Retrieved from Wikipedia

Southern California and Baja California are currently sliding northwards, and in approximately 50 million years, they will become subducted under the Aleutian Trench. So in the very very slight possibility that Los Angeles is still a bustling city 50 million years from now, citizens there will have to move somewhere else.

Charlie