Search results
Results from the WOW.Com Content Network
Obsidian hydration dating (OHD) is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian.. Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping, or breaking off pieces in a controlled manner, such as ...
The Lapita culture, active across a large area of the Pacific Ocean around 1000 BC, made widespread use of obsidian tools and engaged in long distance obsidian trading. The complexity of the production technique for these tools, and the care taken in their storage, may indicate that beyond their practical use they were associated with prestige ...
Magma rises through oceanic crust at mid-ocean ridges. Sheeted dyke complexes are most commonly found at divergent plate boundaries marked by the presence of mid-ocean ridges. These subaqueous mountain ranges are made up of newly created oceanic crust due to tectonic plates moving away from each other.
The surface expressions of subduction zones are arc-trench complexes. On the ocean side of the complex, where the subducting plate first approaches the subduction zone, there is often an outer trench high or outer trench swell. Here the plate shallows slightly before plunging downwards, as a consequence of the rigidity of the plate. [18]
At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin, e.g. the Mid-Atlantic Ridge and East Pacific Rise. As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands, and finally, the plate area increases causing many small volcanoes and ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor.These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from ...
On the morning of Dec. 26, 2004, an estimated 9.2-magnitude earthquake violently shook the seafloor off Indonesia, sending a 100-foot wall of water towards communities around the Indian Ocean.