2 add tidal story from Tolstoy 2005
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The previous answers contain important facts, but neglect recent discoveries. As tobias47n9e says, the increase in observed output over time is an observational effect. As kaberett explains, if you're talking about megayear timescales, Large Igneous Provinces will have a large impact on the timeseries. However, LIP and all continental eruptions (~1km^3 / year) are dwarfed by midocean ridge seafloor eruptions (~3km^3 / year).

Volcanologists have made major progress towards answering your question (are production rates trending? periodic?) over the last few years.

We've learned that:

  • Melting icecaps causes an increase volcanic output, from this paper:
    • Schmidt, Peter, et al. "Effects of present‐day deglaciation in Iceland on mantle melt production rates." Journal of Geophysical Research: Solid Earth 118.7 (2013): 3366-3379.
  • Lowering sea level causes an increase midocean ridge volcanic output, from these papers:
    • Tolstoy, Maya. "Mid‐ocean ridge eruptions as a climate valve." Geophysical Research Letters (2015).
    • Crowley, John W., et al. "Glacial cycles drive variations in the production of oceanic crust." Science 347.6227 (2015): 1237-1240.

The authors attributed these effects to decompression melting. If you remove a weight from above a magma chamber, the pressure in the chamber is reduced, and the melting temperature is lowered, causing an increase in the amount of melt available for eruption. (Personally, I suspect that it's not really decompression melting causing the change in eruption rate but actually just fractures opening and closing.)

The Tolstoy paper claims that if you look at seafloor topography, you see bumps where more lava erupted and piled up higher. Further, it says those bumps correlate with the 100,000 year Milankovitch global climate cycle. So, orbital eccentricity --> sea level --> midocean ridge eruption rate --> seafloor topography. This is a brand new idea and needs much more testing. (Personally, I find the topography thing hard to believe because that topography is probably more fault-controlled than eruption-rate-controlled.)

Tolstoy even claims that low tide causes eruptions! She uses a Schuster test to say that the majority of seafloor eruptions occur during neap tide. However, we don't observe seafloor eruptions very often, so she is making this claim using only 9 data points.

It's currently unknown whether these unloading / loading effects are important at subduction zones or LIP.

You've asked a difficult question which volcanologists have been attempting to understand for decades and will continue to work on for the foreseeable future. In summary, my answer is that cutting-edge research suggests that global eruption rate fluctuates in response to climate via changes in the masses pushing down on magma reservoirs.

The previous answers contain important facts, but neglect recent discoveries. As tobias47n9e says, the increase in observed output over time is an observational effect. As kaberett explains, if you're talking about megayear timescales, Large Igneous Provinces will have a large impact on the timeseries. However, LIP and all continental eruptions (~1km^3 / year) are dwarfed by midocean ridge seafloor eruptions (~3km^3 / year).

Volcanologists have made major progress towards answering your question (are production rates trending? periodic?) over the last few years.

We've learned that:

  • Melting icecaps causes an increase volcanic output, from this paper:
    • Schmidt, Peter, et al. "Effects of present‐day deglaciation in Iceland on mantle melt production rates." Journal of Geophysical Research: Solid Earth 118.7 (2013): 3366-3379.
  • Lowering sea level causes an increase midocean ridge volcanic output, from these papers:
    • Tolstoy, Maya. "Mid‐ocean ridge eruptions as a climate valve." Geophysical Research Letters (2015).
    • Crowley, John W., et al. "Glacial cycles drive variations in the production of oceanic crust." Science 347.6227 (2015): 1237-1240.

The authors attributed these effects to decompression melting. If you remove a weight from above a magma chamber, the pressure in the chamber is reduced, and the melting temperature is lowered, causing an increase in the amount of melt available for eruption. (Personally, I suspect that it's not really decompression melting causing the change in eruption rate but actually just fractures opening and closing.)

The Tolstoy paper claims that if you look at seafloor topography, you see bumps where more lava erupted and piled up higher. Further, it says those bumps correlate with the 100,000 year Milankovitch global climate cycle. So, orbital eccentricity --> sea level --> midocean ridge eruption rate --> seafloor topography. This is a brand new idea and needs much more testing. (Personally, I find the topography thing hard to believe because that topography is probably more fault-controlled than eruption-rate-controlled.)

It's currently unknown whether these unloading / loading effects are important at subduction zones or LIP.

You've asked a difficult question which volcanologists have been attempting to understand for decades and will continue to work on for the foreseeable future. In summary, my answer is that cutting-edge research suggests that global eruption rate fluctuates in response to climate via changes in the masses pushing down on magma reservoirs.

The previous answers contain important facts, but neglect recent discoveries. As tobias47n9e says, the increase in observed output over time is an observational effect. As kaberett explains, if you're talking about megayear timescales, Large Igneous Provinces will have a large impact on the timeseries. However, LIP and all continental eruptions (~1km^3 / year) are dwarfed by midocean ridge seafloor eruptions (~3km^3 / year).

Volcanologists have made major progress towards answering your question (are production rates trending? periodic?) over the last few years.

We've learned that:

  • Melting icecaps causes an increase volcanic output, from this paper:
    • Schmidt, Peter, et al. "Effects of present‐day deglaciation in Iceland on mantle melt production rates." Journal of Geophysical Research: Solid Earth 118.7 (2013): 3366-3379.
  • Lowering sea level causes an increase midocean ridge volcanic output, from these papers:
    • Tolstoy, Maya. "Mid‐ocean ridge eruptions as a climate valve." Geophysical Research Letters (2015).
    • Crowley, John W., et al. "Glacial cycles drive variations in the production of oceanic crust." Science 347.6227 (2015): 1237-1240.

The authors attributed these effects to decompression melting. If you remove a weight from above a magma chamber, the pressure in the chamber is reduced, and the melting temperature is lowered, causing an increase in the amount of melt available for eruption. (Personally, I suspect that it's not really decompression melting causing the change in eruption rate but actually just fractures opening and closing.)

The Tolstoy paper claims that if you look at seafloor topography, you see bumps where more lava erupted and piled up higher. Further, it says those bumps correlate with the 100,000 year Milankovitch global climate cycle. So, orbital eccentricity --> sea level --> midocean ridge eruption rate --> seafloor topography. This is a brand new idea and needs much more testing. (Personally, I find the topography thing hard to believe because that topography is probably more fault-controlled than eruption-rate-controlled.)

Tolstoy even claims that low tide causes eruptions! She uses a Schuster test to say that the majority of seafloor eruptions occur during neap tide. However, we don't observe seafloor eruptions very often, so she is making this claim using only 9 data points.

It's currently unknown whether these unloading / loading effects are important at subduction zones or LIP.

You've asked a difficult question which volcanologists have been attempting to understand for decades and will continue to work on for the foreseeable future. In summary, my answer is that cutting-edge research suggests that global eruption rate fluctuates in response to climate via changes in the masses pushing down on magma reservoirs.

1
source | link

The previous answers contain important facts, but neglect recent discoveries. As tobias47n9e says, the increase in observed output over time is an observational effect. As kaberett explains, if you're talking about megayear timescales, Large Igneous Provinces will have a large impact on the timeseries. However, LIP and all continental eruptions (~1km^3 / year) are dwarfed by midocean ridge seafloor eruptions (~3km^3 / year).

Volcanologists have made major progress towards answering your question (are production rates trending? periodic?) over the last few years.

We've learned that:

  • Melting icecaps causes an increase volcanic output, from this paper:
    • Schmidt, Peter, et al. "Effects of present‐day deglaciation in Iceland on mantle melt production rates." Journal of Geophysical Research: Solid Earth 118.7 (2013): 3366-3379.
  • Lowering sea level causes an increase midocean ridge volcanic output, from these papers:
    • Tolstoy, Maya. "Mid‐ocean ridge eruptions as a climate valve." Geophysical Research Letters (2015).
    • Crowley, John W., et al. "Glacial cycles drive variations in the production of oceanic crust." Science 347.6227 (2015): 1237-1240.

The authors attributed these effects to decompression melting. If you remove a weight from above a magma chamber, the pressure in the chamber is reduced, and the melting temperature is lowered, causing an increase in the amount of melt available for eruption. (Personally, I suspect that it's not really decompression melting causing the change in eruption rate but actually just fractures opening and closing.)

The Tolstoy paper claims that if you look at seafloor topography, you see bumps where more lava erupted and piled up higher. Further, it says those bumps correlate with the 100,000 year Milankovitch global climate cycle. So, orbital eccentricity --> sea level --> midocean ridge eruption rate --> seafloor topography. This is a brand new idea and needs much more testing. (Personally, I find the topography thing hard to believe because that topography is probably more fault-controlled than eruption-rate-controlled.)

It's currently unknown whether these unloading / loading effects are important at subduction zones or LIP.

You've asked a difficult question which volcanologists have been attempting to understand for decades and will continue to work on for the foreseeable future. In summary, my answer is that cutting-edge research suggests that global eruption rate fluctuates in response to climate via changes in the masses pushing down on magma reservoirs.