Showing posts with label tectonic plates. Show all posts
Showing posts with label tectonic plates. Show all posts

May 22 – Tectonic Blast! Tectonic Crack!

Posted on May 22, 2019

When we talk about Natural Disasters, we are often talking about terrible weather:

Brutal sandstorms, violent lightning strikes, killer tornadoes, deadly blizzards, destructive hurricanes (or typhoons or  cyclones; all three are basically the same thing).


But there are Natural Disasters that are not weather-related. Instead, they have to do with tectonic forces.

Tectonic forces are those that originate below the Earth's surface as a result of the movement of the continental and undersea plates. The two main disasters in the "tectonic" category are volcanoes and earthquakes.

The Earth's crust is made up of a lot of different
tectonic plates that move around!



Volcanoes

On this date in 1915, Mount Lassen erupted violently, ejecting rock and pumice, ash and gas. The ash and gas formed a column more than 30,000 feet tall - it could be seen from as far away as 150 miles! A large, deep crater formed at the mountain's summit. Only three square miles of nearby region were devastated, but mudflows and pyroclastic flows of hot ash, pumice, and rock reached many more miles.




Don't worry, Mount Lassen's eruption didn't kill people, although it did cause a few minor injuries among people escaping the mudflows. The thing about volcanoes is that they commonly are rocked by earthquakes before they erupt, and they often vent steam or show other signs of being active before they blow big. Lassen woke up on May 30, 1914, after 27,000 years of being dormant, and there were about 400 eruptions between 1914 and 1921, including the one we commemorate today (the biggest eruption of them all).

Because it was the first U.S. volcano to erupt in the 1900s, Lassen Peak's eruptions and activity were very well photographed and studied. 

Lassen Volcanic National Park is a lovely place to visit -
although of course scientists monitor tectonic activity
and earthquakes in case the volcano shows signs
of becoming active once again!
When two plates collide, volcanoes can
form above the collision zone.

Earthquakes

The most powerful earthquake ever recorded occurred in Chile on this date in 1960. It ranged from 9.4 to 9.6 on the "moment magnitude scale" (expressed in the terms we are pretty familiar with from the Richter Scale). 

Unfortunately, the "Great Chilean Earthquake"
and the tsunamis that resulted from the quakes
caused a lot of damage and many deaths.

Damage in Hawaii, more than 6,000 miles
(10,000 km) away from the earthquake's
origin.
The earthquake set off tsunamis that did more damage, even, than the original 10-minute-long shake. The tsunamis kicked off waves up to 82 feet tall; a tsunami devastated Hilo, Hawaii, several local tsunamis battered the Chilean coast, and high waves affected faraway spots like the Philippines and Japan!

Like the volcano, this powerful earthquake had some warning - but the warning was an earlier almost-as-powerful earthquake! On May 21, 1960, an 8.1 quake rocked Chile. On May 22, 1960, two more strong earthquakes hit in the same locale as the first; fifteen minutes after the third quake, the monster 9.4 quake hit around 280 miles (460 km) away from the first three.

Smaller aftershocks shook Chile until June 6.

Just as the collisions of tectonic plates
can cause volcanoes, these collisions
can also cause earthquakes.


Tectonic plates cause what has been
called "continental drift" - the slow
changing of the number and position 
of the continents.




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June 20 – Martyrs' Day in Eritrea

Posted on June 20, 2016

I've talked a bit about the 30-year war of independence in Eritrea in an earlier post. Today is set aside to remember the tens of thousands of people who died during that generation-long struggle.

Unfortunately, the two nations involved in that war -- Ethiopia and Eritrea -- are still skirmishing along the border! Like, when I googled “Eritrea” just now, there was a news item about a deadly battle from just a few hours ago!



When-oh-when will peace reign in that region?

Rather than go back through the depressing stuff about humans vs. humans, with way too much killing along the border, I thought I would talk about the Danakil Depression, on the border between Eritrea and Ethiopia.

The Danakil Depression has nothing to do with the sad kind of depression, nor with killing (despite its name). Instead, it is a very low-lying area, a depression in the Earth's crust.

The Depression is there because, in the Horn of Africa, where Eritrea is located, several tectonic plates are moving apart from one another, more quickly than is usual for geological movement. The Horn of Africa is eventually going to be ripped off of the rest of Africa, and we are witnessing the birth of a new ocean.

You probably know that the rocky crust of the Earth is not solid, but rather made up of plates of different sizes and shapes. They slo-o-o-o-o-owly ride on top of the hotter, more mobile mantle.


In some places, two plates are pulling away from each other, moving apart. Magma rushes in to fill the widening gap. When this happens on a continent, like Africa, a low rift valley is formed. Eventually, most rift valleys fill up with water and eventually eventually most become steadily widening oceans!


Here you can see some of the directions in which plates are pulling apart in that part of Africa.


The Danakil Depression is the hottest place on Earth, when you look at year-round average temperatures. It is one of the lowest places on Earth (330 feet below sea level, or 100 feet below sea level), and it has no rainfall most of the year.

It sounds a bit like hell, doesn't it? But...when you look at the magma crater lakes in the Danakil Depression's active volcano, and you consider the fact that the hot springs smell like sulfur...


I mean, come on! Look at this place!!!




 


There's not much life in this tectonically active region. Any microorganisms that live there are extremophiles (organisms that love extreme environments), most of them thermophiles (organisms that love really hot environments).

Still, even though the Danakil Depression isn't exactly lush with lifeforms, understanding the biology going on there may be helpful in understanding the sorts of lifeforms we might find on other planets and moons. Also, this area is called the cradle of the hominids because Donald Johanson and his colleagues discovered the famous Australopithecus skeleton we call Lucy there. 




Also on this date:


Solstice







Baseball executive Branch Rickey's birthday































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July 27 – Happy Birthday, Thomas George Bonney

Posted on July 27, 2014

So...if you learn a lot about something while having fun doing your hobby, you too might end up with a university job teaching that something, a Wikipedia article about yourself, and a lake in Antarctica named after you!

Born on this date in 1833, the English geologist Thomas George Bonney was a math teacher who loved to hike around alpine (high mountain) regions, studying the rocks there.

He got so knowledgeable about alpine geology, he became a geology lecturer at a college and later a professor of geology at a university. He also became the president of the Alpine Club.

Bonney also wrote a biography of geologist Charles Lyell, who was the most important geologist of his time. Lyell came up with the concept of uniformitarianism, which is the idea that the Earth was shaped by the same forces and processes that we see happening today. Rather than assuming that the Earth's landforms were created very suddenly by short-term, violent events like a catastrophic global flood, Lyell suggested that they were created slowly and gradually by processes such as erosion, which we see occur now. Lyell was one of the first geologists to realize that the Earth was older than 300 million years.

Lyell was a friend of and important influence on biologist Charles Darwin.

The word alpine comes from the Alps

When we talk about alpine animals, alpine plants, and alpine geology being the animals, plants, and rocks found on high mountains, we are using a word coined by Europeans for the highest mountains in Europe: the Alps.

The Alps are a mountain range that stretch from Austria and Slovenia, in the east, through Switzerland, Liechtenstein, Italy, Monaco, Germany and France, in the west.








Like many mountain ranges, the Alps were created when two tectonic plates collided. Remember, geology has a lot of very slow (yet unstoppable) processes, and the collision of two plates is one of them. It's not a dramatic SMASH! BANG! collision -- but it goes on and on year after year after year after thousands and millions of years.

In the case of the Alps, the African plate and the Eurasian plate moved slowly toward one another, probably at about the rate of fingernail growth. They collided while traveling toward one another at a rate of less than an inch to a few inches PER YEAR.

(Of course, once in a while tectonic plates move quickly, slipping past each other in a juddery, skittery event called an earthquake. But that's generally when plates are moving alongside each other.) 

In the case of colliding plates, it's hard to see any change within a human lifetime. But as they collide, the plates push upwards in a series of folds, forming mountains over millions of years.

Here is what is special about the Alps: 

They are the most densely populated mountain area in the world.

The Alps are middle aged mountains. (For comparison, the Rockies and Himalayas are considered young – at 10 to 25 million years of age. The Urals and Appalachians are old, at more than 200 million years of age. The Alps began to form about 40 million years ago.)

About 11 million people live in the Alps, making their living through forestry, pasturing sheep, cattle, and other animals, and of course tourism. Ski resorts and other winter tourism is especially popular, but in the summer the Alps are filled with hikers and walkers, cable-car riders, and para-gliders.



Because of the huge numbers of tourists and the large all-year population, the Alps is considered the most threatened mountain chain in the world.

I am thrilled to inform you that, although I have only ever been to the Alps in the summer, I was up high enough during a storm that it snowed on us! I never thought I would get to say that I was snowed on in the Alps!
The world-famous Matterhorn










Tourists can even enjoy the INSIDES
of the Alps. This tunnel was carved
into a glacier. I visited tunnels and under-
ground caves of a salt mine in the Alps.

Also on this date:



Walk on Stilts Day 




























Plan ahead:

Check out my Pinterest boards for:
And here are my Pinterest boards for:

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