Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
4 online now:
Newest Member: popoi
Post Volume: Total: 915,815 Year: 3,072/9,624 Month: 917/1,588 Week: 100/223 Day: 11/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Heat release from tectonic friction
edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 62 of 102 (684440)
12-17-2012 3:30 PM
Reply to: Message 59 by TrueCreation
12-17-2012 1:37 AM


Re: Back of envelope calculation
Well it is precisely the 'surrounding rocks' which are cooling. Here is a 2D (average transect with age) tomographic inversion for upper mantle temperature over Pacific oceanic lithosphere as a function of lithospheric age: http://ciei.colorado.edu/...piro_research_files/image003.jpg
This thermal structure is clearly a consequence of gradual conductive cooling of the upper mantle with age, corroborated by many other geophysical observations in addition to seismic tomography. No other physical mechanism can account for these observations.
TC, you are touching on an important point here. IMHO, the frictional heating is almost irrelevant. The reason is that all we have done on the oceanic lithosphere formation and conveyance, is convert the original convective magmatic heat from the mantle into conductive heat in the crust which ulltimately flows to the ocean and atmosphere and eventually radiates into space.
Simply put, the earth is cooling. Any frictional heat is minor and transient. The end result is the same: a cooling planet.
I suggest the way to attack the heat problem is to calculate the average current heat flow from the earth and project that 4.5 ga into the past (this would be a minimum number since the heat flows of the distant past were certainly much higher - so we are only getting an end-member here).
Okay, now compress that amount of heat into 6ky and see what happens.
By the way, I'm not so sure that your statement about where the heat-forming radioelements are found is correct. While many of the elements are found in continental crust, where we can extract them, there is some consensus that the core is another concentration of radionuclides such as thorium and uranium. After all, what causes heating of the mantle plumes?

This message is a reply to:
 Message 59 by TrueCreation, posted 12-17-2012 1:37 AM TrueCreation has replied

Replies to this message:
 Message 66 by TrueCreation, posted 12-18-2012 4:14 AM edge has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024