ash layer

Then, after more millions of years, rivers cut down through the rock and into the ash layers below.

Ash layers in the core have been identified by their sulfur content.

There was a continuous ash layer in the centre of the anteroom.

It is occasionally found in ash layers within marine sediments.

The lack of a significant ash layer associated with this event indicates that it was a small eruption.

During early excavations of the site, occasional voids in the ash layer had been found that contained human remains.

They are also used to date volcanic ash layers within or overlying paleoanthropologic sites.

During the excavation, plaster was used to fill in the voids between the ash layers that once held human bodies.

Thin volcanic ash layers may occur in the British Columbia foothills.

In a sedimentary sequence the associated material within the ash layer can be dated, giving a date for the eruption.

Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater.

The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers.

The ash layer now forms a useful stratigraphic marker layer throughout Peru.

A chocoyo is a type of bird which is often found nesting in the relatively soft ash layer.

Artefacts found in the volcanic ash layers show that Aborigines were living in the area at the time of the eruption.

Volcanic ash layers occur in the Bass Formation.

The Bass Formation also contains stromatolite beds and thin volcanic ash layers.

Volcanic eruptions may be detected by visible ash layers, acidic chemistry, or electrical resistance change.

Obsidian debitage continued below these ash layers, suggesting that the area was used as a refuse deposit for a prolonged period.

Volcanic eruptions leave identifiable ash layers.

Numerous archaeological features, including pits, postmolds, hearths, firebeds and ash layers, have also been identified.

Eight ash layers have been identified in the central Greenland ice core GRIP.

Volcanic ash layers are present in the Austin chalk, and were deposited by wind from distant erupting volcanoes around 86 mya.

The researchers dated mineral crystals in volcanic ash layers above and below layers of river sediments that contain the early human bones.

Sieges and conquest: ballista bolts, ash layers, vitrified stones, burnt post holes.