How Does the Mantle Melt in Geology?

[davenn]

I don't think it was as clearly explained to me, as what this video does, when I did geology at university



Published on Sep 25, 2017
Thanks a lot to K. Shaw, who helped us to correct our title!
Here is the latest animation from UTD GSS, titled: "Three Great Ways to Melt the Mantle." It explains how the mantle melts using an animated P/T diagram, and relates melting to tectonic setting. Please leave comments, suggestions, criticisms, and questions below.
If you need caption, please click 'CC' button underneath the video screen.
UTD GSS Product. Lochlan Vaughn (Producer). Robert J Stern (Director). Special thanks to Julian Pearce, who provide his knowledge and ideas to this video.
https://utdgss2016.wixsite.com/utdgss

To See the Caption please check the link below:
https://utdgss2016.wixsite.com/utdgss...

Learn more Geoscience at UTD Geoscience Studio Website
https://utdgss2016.wixsite.com/utdgss

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cheers
Dave

 

[Bystander]

Thank you.

 

[davenn]

Thank you.

really clear and easy to follow,

 

[BillTre]

That's an excellent explanatory video!
Great Find @davenn.

Here is a pretty good one I found on that vid's youtube page:

 

[davenn]

That's an excellent explanatory video!
Great Find @davenn.

Here is a pretty good one I found on that vid's youtube page:

Ah hah, I downloaded that one several days ago
Thanks for posting …. the others may not have seen it

I have downloaded dozens of videos referencing the latest Hawai'i activity and a few other doco's
that talk about the Hawai'i volcanics in general, like that one you posted.

There is just so much good info out there ( ohhhh there's some total rubbish as well hahaha)

Dave

 

[BillTre]

This stuff is really interesting, the more you get into the detailed situations of what actually is occurring.

Maybe you could through together a reading veiwing list.

 

[OmCheeto]

really clear and easy to follow,

For you maybe...
Do you have any idea how many times non-geologists have to stop the video to figure out what some of those things are?
No?
Well..., LOTS!

I had to watch it 4 times, and I'm still confused about some of the details.

Maybe you could through together a reading veiwing list.

I liked "Physics Girl"'s video.


Why Hawaii's volcano is so UNUSUAL
Physics Girl
Published on Mar 16, 2017

 

[davenn]

I had to watch it 4 times, and I'm still confused about some of the details.

OK, no probs.
give a specific thing or 2 for a start that you are not sure of and we can work through them with you
Others may be in the same "boat" as you and also find it helpful

I liked "Physics Girl"'s video.

yup, a good video, putting things in an easy to understand way

Dave

 

[Mark44]

I've been looking at a couple of books in the Roadside Guide to Geology series -- the books on Washington, my state, and Oregon, just south of Washington. I enjoyed the Physics Girl video, but was surprised that omitted the basalt floods that came out of a volcano about 30 Million years ago in SE Washington and NE Oregon, in the area around La Grande, OR. As it turns out, a large fraction of Washington is covered by the Columbia River Basalts, and the majority of Oregon is volcanic in origin. From my reading, the basalt floods hereabouts represent some of the largest outflows of basalt in the world, near to or exceeding those of the Deccan Plain in India and those in Siberia (which I believe are called the Siberian Traps). In some places the basalt is as much as 10,000' thick, representing many eruptions.

One of the things not mentioned in the video is the types of lava that are emitted by a volcano. Basalt tends to be very low in viscosity, and can flow for many miles. The basalt coming out of the La Grande volcano flowed about 200 miles, all the way to the mouth of the Columbia on the Pacific. Other volcanos can emit andesite or rhyolite, types of rock that are chemically similar, but differing in their relative silica concentration. Basalt is at the low end in silica content, andesite in the middle, and rhyolite the highest.

Volcanos that emit basalt tend to be relatively flat, so-called shield volcanos, like Mauna Loa and Mauna Kea on the Big Island of Hawaii. Volcanoes that emit andesite, which is more viscous than basalt, tend to form composite volcanoes, having a more conical appearance. Rhyolite is the most viscous, and if it absorbs a lot of water on its way up through the crust, can be very explosive, sometimes destroying the volcano, as was the case with Mt. Mazama in Oregon, the caldera of which is called Crater Lake.

The composition of the lava is determined mostly by the type of rock that got melted. Basalt comes from the dense sea floor melting, and rhyolite comes from the melting of a section of the much lighter continental crust. There are numerous sea floor spreading zones, with each size marking a boundary of a different plate, As the margins of the plates move away from the spreading zone, the other ends of the plates are subducted into a trench at the other end of the plate. The heavier sea floor always dives under the lighter continental crust. As the subducted plate goes deeper into the mantle, it is heated up, and sends up blobs of magma, similar to the lava lamp that was shown in the video.

I'm not a geologist, so I might not be 100% accurate on my description, but I am an interested amateur, having spent a lot of time climbing the volcanoes in my state, Oregon and Northern California.

 

[davenn]

I enjoyed the Physics Girl video, but was surprised that omitted the basalt floods that came out of a volcano about 30 Million years ago in SE Washington and NE Oregon, in the area around La Grande, OR. As it turns out, a large fraction of Washington is covered by the Columbia River Basalts, and the majority of Oregon is volcanic in origin. From my reading, the basalt floods hereabouts represent some of the largest outflows of basalt in the world, near to or exceeding those of the Deccan Plain in India and those in Siberia (which I believe are called the Siberian Traps). In some places the basalt is as much as 10,000' thick, representing many eruptions.

Yes, the ones in the Oregon region are pretty extensive. I remember taking a good few photos in my trips up the Colombia River gorge in years gone by.
I guess, the guy in the video couldn't mention everything, as could be seen, it was all done "on the fly".

Overall a good fun explanation, tho I disagree with a couple of his comments...
1) Basaltic magma/lava DOESNT erupt explosively as they tried to depict. Yes, you can get massive lava fountains, but that are not explosive eruptions like say Mt St Helens and the other Cascade volcanoes, Mt Pinatubo etc.

2) I and most geologists will argue against the Deccan Traps volcanics causing the K-T boundary mass extinction. Even tho they are of the right age.
The primary extinction mechanism was still the meteor/asteroid impact in in the Yuccatan Penin., Mexico. From my readings in years gone by ( I would have to do some searching again). There is a theory that that impact caused the Deccan Traps eruptions with the focussing of seismic waves from the impact focussing on the other side of the world in the general region that India was at that time ( taking continental drift into account).
Rather the inference is the impact caused most of the extinction event with added help from the D.T volcanics.

 

[davenn]

the books on Washington, my state, and Oregon, just south of Washington. I enjoyed the Physics Girl video, but was surprised that omitted the basalt floods that came out of a volcano about 30 Million years ago in SE Washington and NE Oregon, in the area around La Grande, OR. As it turns out, a large fraction of Washington is covered by the Columbia River Basalts, and the majority of Oregon is volcanic in origin. From my reading, the basalt floods hereabouts represent some of the largest outflows of basalt in the world, near to or exceeding those of the Deccan Plain in India and those in Siberia (which I believe are called the Siberian Traps). In some places the basalt is as much as 10,000' thick, representing many eruptions.

Some background for Columbia River Basalt Group

( We can lower those figures a bit ) they should be accurate in the wiki article …. there's a mass of good quality cited references

from Wiki
https://en.wikipedia.org/wiki/Columbia_River_Basalt_Group

During the middle to late Miocene epoch, the Columbia River flood basalts engulfed about 163,700 km² (63,200 sq mi) of the Pacific Northwest, forming a large igneous province with an estimated volume of 174,300 km³ (41,800 cu mi). Eruptions were most vigorous 17–14 million years ago, when over 99 percent of the basalt was released. Less extensive eruptions continued 14–6 million years ago.[1]

Erosion resulting from the Missoula Floods has extensively exposed these lava flows, laying bare many layers of the basalt flows at Wallula Gap, the lower Palouse River, the Columbia River Gorge and throughout the Channeled Scablands.

The Columbia River Basalt Group is thought to be a potential link to the Chilcotin Group in south-central British Columbia, Canada.[2] The Latah Formation sediments of Washington and Idaho are interbedded with a number of the Columbia River Basalt Group flows, and outcrop across the region.

Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as 40Ar/39Ar dating, which can be used to identify the date of solidifying basalt. In the CRBG deposits 40Ar, which is produced by 40K decay, only accumulates after the melt solidifies.[3]

Other flood basalts include Deccan Traps (late Cretaceous period) that cover an area of 500,000 km2 (193,051 sq mi) in west-central India and Siberian Traps (late Permian) that cover 2 million km² (800,000 sq mi) in Russia.

So, substantially smaller areas covered than either the Deccan and Siberian Traps

Just looking for the volume erupted for the later 2 for comparisons

1) Columbia River flood basalts; 163,700 km² (63,200 sq mi); with an estimated volume of 174,300 km³

2) Deccan Traps; cover 500,000 km² (193,051 sq mi); have a volume of c. 1,000,000 km3

Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India (17°–24°N, 73°–74°E) and are one of the largest volcanic features on Earth. They consist of multiple layers of solidified flood basalt that together are more than 2,000 m (6,600 ft) thick, cover an area of c. 500,000 km² (200,000 sq mi),[1] and have a volume of c. 1,000,000 km³ (200,000 cu mi).[2] Originally, the Deccan Traps may have covered c. 1,500,000 km² (600,000 sq mi),[3] with a correspondingly larger original volume.

3) Siberian Traps; cover 2 million km² (800,000 sq mi); with a volume of around 4 million km³.

The Siberian Traps (Russian: Сибирские траппы, Sibirskiye trappy) is a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The massive eruptive event that formed the Traps is one of the largest-known volcanic events that has occurred in the last 500 million years.

The eruptions continued for roughly two million years and spanned the P–T boundary, or the Permian–Triassic boundary, which occurred between 251 to 250 million years ago.[1][2]

Large volumes of basaltic lava covered a large expanse of Siberia in a flood basalt event. Today, the area is covered by about seven million km² of basaltic rock, with a volume of around 4 million km³.[3]

Siberian is oldest and largest, then Deccan, then Columbia River Group ( which is tiny in comparison )Regards
Dave

 

[davenn]

2) I and most geologists will argue against the Deccan Traps volcanics causing the K-T boundary mass extinction. Even tho they are of the right age.
The primary extinction mechanism was still the meteor/asteroid impact in in the Yuccatan Penin., Mexico. From my readings in years gone by ( I would have to do some searching again). There is a theory that that impact caused the Deccan Traps eruptions with the focussing of seismic waves from the impact focussing on the other side of the world in the general region that India was at that time ( taking continental drift into account).
Rather the inference is the impact caused most of the extinction event with added help from the D.T volcanics.

this paper reference comments on "some" of the deccan volcanics

https://pubs.geoscienceworld.org/gs...gering-of-the-largest-deccan-eruptions-by-the

other papers

http://Earth'sky.org/earth/dinosaur-killing-asteroid-caused-indias-deccan-traps

https://www.sciencedaily.com/releases/2015/05/150504141901.htm

from Wiki link on the Deccan Traps

Effect on mass extinctions and climate[edit]
The release of volcanic gases, particularly sulphur dioxide, during the formation of the traps contributed to climate change. Data points to an average drop in temperature of 2 °C in this period.[6]

Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction).[7] It was theorized that sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to the K–Pg, as well as other mass extinctions.[8] However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in North America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter).[9]

Work published in 2014 by geologist Gerta Keller and others on the timing of the Deccan volcanism suggests the extinction may have been caused by both the volcanism and the impact event.[10][11] This was followed by a similar study in 2015.[12][13]

Dave