From 1.7 to 0.7 billion years ago nothing much happened on Earth . It was “ characterize by environmental , evolutionary and lithospheric stability that contrasts with the spectacular changes in preceding and come through eras , ” as a paper inGeologyputs it . But the paper goes further , offering an account for this pause , while complementary grounds hint continental drift may be speeding up .
You ’ve got to love the geologist unforced to label a planetary era the “ boring billion ” . Others call it the Earth ’s in-between age , but however you want to entitle it an explanation is call for . Plentyhave beenofferedwithout gaining overwhelming support .
The pause is thought to have been take to an conclusion by the a series of glaciation , where the entire Earthmayhave frozen , after which the wonderfully namedAvalon Explosionsaw complex multicellular being appear in the fossil platter .
However , it is not just biological science that stalled during theMesoproterozoicera andTonianperiod . The theme notes , “ The period is marked by … a lack of orogenic gold and volcanic - hosted monumental sulphide depository , and an absence of frosty deposits and iron formation . ”
The paper ’s authors , Professors Peter Cawood and Chris Hawkesworth , both of the University of St Andrews , reckon these are connect . They debate , “ These trends are impute to a relatively stable continental assemblage that was initiated during assembly of the Nuna supercontinent by ca . 1.7 Ga and continued until dissolution of its tight bear on replacement , Rodinia , ca . 0.75 Ga. ”
" Before 1.7 billion year ago , the Earth ’s crust would have been substantially hotter , meaning that continental plate motion may have been regulate by different rule to those that operate today , " say Cawood . The mantle was too hot for continental stuff to slither into it as now happens at plate boundary . therefore , once a supercontinent formed nothing could part it apart .
A single giant continent and even larger ocean did n’t declare oneself the diverse niche that be given to drive organic evolution . Moreover , the creation and death of mountain ranges that come with continents in hit passing pulsing of nutrient into the oceans with major result on the variety of liveliness there .
Cooler temperature are normally associated with boil down movement , but in this case Cawood says we saw the turnaround .
" Seven hundred and fifty million years ago , the crust reached a tip where it had cooled sufficiently to allow modernistic day home plate tectonics to begin turn , in picky allowing subduction zones to form ( where one home base of the crust moves under another ) , ” says Cawood . Meanwhile the continent was growing downwards , add together bulk that meant that when it pulled asunder there was even more of it to be driven into the mantle .
“ This increase in natural action could have kick - started a ten thousand of changes include the break - up of Rodinia and changes to levels of primal element in the air and seas , which in twist may have induce evolutionary change in the lifetime forms present . " says Cawood . The continental changes could also have move the mood .
At the Goldshmidt geochemistry conference this month , Professor Kent Condie of New Mexico Techpresented evidencefrom sovereign research in keep with Cawood and Hawesworth ’s ending . “ Our event dispute the view that the rate of photographic plate move is static over time , " said Condie . " The interpretation of information from many other disciplines such as stable isotope geochemistry , palaeontology and paleoclimatology in part rely on the assumption that the movement pace of the Earth ’s crust is constant . " Instead he find grounds from the geomagnetic record to suggest continents have sped up with prison term , and may be continuing to do so .
" We now urgently need to compile further data on vital clock time periods to see more about the constraint on photographic plate speed and the absolute frequency of collision between continental blocks , " Condie supply .
