Electron micrograph showing mitochondria in the mantle layer of control and MeHg-treated embryos.

This is the mantle layer, where temperatures can reach more than 1,371 [degrees] c, hot enough to melt rock that can extend down to more than 3,200 kilometers.

Anatomical characteristics of mantle in plan views: Outer mantle layer parenchymatous, cells 11-12 um in length and 11.5 um wide, no matrix material, no ornamation of cells, cell contents clear, brownish cells, cells rounded to irregular shape (Fig.

Iceland, the Azores, and the Galapagos are examples of these "hotspot" islands - so named because they are believed to form above small regions scattered around the earth where unusually hot rocks rise from deep inside the mantle layer.

Geophysicists estimate that some 80 percent of its heat comes from the decay of radioactive elements distributed throughout the mantle layer. The remaining fraction of heat comes from the core below.

Peridotites originate in the mantle layer, offering scientists a window into the conditions beneath the tectonic plates.