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View Full Version : Baikal Rift Zone is Becoming More Active Again



Squink
2015-Feb-13, 03:49 PM
Siberian Times:
Is a potentially catastrophic earthquake on the way in Siberia? (http://siberiantimes.com/science/opinion/features/f0058-is-a-potentially-catastrophic-earthquake-on-the-way-in-siberia/)
More than 50 major tremors have been registered around the north of Lake Baikal this year, varying in magnitude from 3.0 to 5.0 on the Richter Scale.

Experts from around the world have been monitoring the situation, with some saying the whole Baikal rift zone – which covers a massive territory including the Irkutsk region and the Republic of Buryatia – is going through a phase of rising tectonic activity.
...
Each year the shores of Lake Baikal move further apart by about 5mm, and there is a theory that the rift will eventually split the land mass in 650 million years’ time.
Odd spot for a rift (https://www.google.com/maps/@56.4407118,85.5534561,3z). I'm not seeing a clear path for propogation to the south.

Ara Pacis
2015-Feb-15, 05:03 PM
Don't rifts tend to start as triple junctions? Could the Indian plate collision be deforming it? Could some of this be attributed to post-glacial rebound?

Romanus
2015-Feb-16, 02:44 PM
I read somewhere that the Baikal rift is distantly related to the impact of India into Asia, perhaps an effect of torque. In any event, I'd expect a lot more uplift and magmatic activity from a potential spreading center, but I admit that we're hindered by the fact that we've never seen an actual spreading center form.

Ara Pacis
2015-Feb-16, 10:30 PM
I read somewhere that the Baikal rift is distantly related to the impact of India into Asia, perhaps an effect of torque. In any event, I'd expect a lot more uplift and magmatic activity from a potential spreading center, but I admit that we're hindered by the fact that we've never seen an actual spreading center form.

Could the rift not have penetrated through the crust to where magma exists and could well up? Could the rift be cause not by pulling apart of a slab or a punching through of a mantle plume, but by flexing the crust (like breaking a baguette in half where the break propagates downward?

geonuc
2015-Feb-17, 12:44 PM
Don't rifts tend to start as triple junctions?
My geological training is a bit dated, but yes, most continental rifts are part of triple junctions. But not all. The Baikal Rift appears to be in an extensional terrane associated with the Asia/India collision. No triple junction.

geonuc
2015-Feb-17, 05:18 PM
Don't rifts tend to start as triple junctions?
My geological training is a bit dated, but yes, most continental rifts are part of triple junctions. But not all. The Baikal Rift appears to be in an extensional terrane associated with the Asia/India collision. No triple junction.

I'm going to amend my contribution to the thread to point out that there are currently only a few active continental rift zones that I know of: including the Baikal, the Rio Grande and the East African. The latter is an extensive system of faults including rifts and a triple junction. The Basin & Range province in western North America is also sort of a rift, but a diffuse one with extension taking place over a wide area. No triple junction there.

So, I retract my earlier assertion: I don't know if continental rifts tend to start with triple junctions or not.

Eclogite
2015-Feb-21, 11:58 AM
So, I retract my earlier assertion: I don't know if continental rifts tend to start with triple junctions or not.Standard plate tectonic theory, invoking rigid plates and spherical geometry would - to my understanding - require that rifts that result in plate separation necessarily begin with triple junctions. However, standard theory is a bit of a simplification.

Pertinent question: are you using continental rift to refer to large scale rifts in continental crust, or are you including smaller scale features? If the latter, then many examples spring to mind. Ah - I self correct: you specified active rift zones. The examples I had in mind are effectively dead, though - like the Midland Valley of Scotland - may still experience minor tectonic activity.

I wonder if the activity is not reflecting strike slip movement. If this is a diverging boundary I would not expect any large seismic event to result. I stand ready to be corrected, but divergent zones are not the subject of major quakes, unless a strike slip motion is involved.

geonuc
2015-Feb-22, 10:01 AM
I wonder if the activity is not reflecting strike slip movement. If this is a diverging boundary I would not expect any large seismic event to result. I stand ready to be corrected, but divergent zones are not the subject of major quakes, unless a strike slip motion is involved.

I believe you are correct in that purely extensional boundaries don't tend to generate large seismic events. And from what I've seen online in papers, the Baikal is pretty close to purely extensional. There are large transform faults that bound the zone to the NE and SW. But right at the lake, its all normal faulting. In that sense, it resembles a segment of an oceanic ridge. It may be that whatever recent activity has occured is just those normal faults moving. I haven't found any data on the recent magnitude 5 earthquakes the OP's link mentions that would characterize the movement.