Question

What are the limitations to earths mantle?

Answer 1

Humans have not been able to travel more than a few miles beneath Earth's surface because of the intense heat and pressure. For the same reasons, humans have not been able to travel into the mantle. Temperatures in the mantle range from 1600 degrees Fahrenheit at the top to 4000 degrees Fahrenheit near the bottom.

Answer 2

The scale of mantle heterogeneities has been debated ever since the first observations of isotopic variations along mid-oceanic ridges1,2. Subsequent studies on lead and strontium isotopic variations along the Mid-Atlantic Ridge3–5 have shown that these isotopic compositions may vary with a major wavelength of ∼100–1,000 km. The immediate question is that of the scale (if any?) at which one may consider a piece of suboceanic mantle under a ridge to be homogeneous. We have studied two segments of oceanic ridges at the scale of a few kilometres. One of these portions of oceanic ridge, the CYAMEX zone in East Pacific Rise is typical, with a strongly ‘depleted’ chemistry. The other one, with an ‘intermediate’ chemistry, is the FAMOUS zone of the Mid-Atlantic Ridge. Our results show isotopic homogeneity for both zones even though small Pb variations persist on a small scale.