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en.wikipedia.org/wiki/Volcanic_rock

Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it differs .... "Global geologic maps are tectonic speedometers—Rates of rock cycling from area-age frequencies". Geological Society of America Bulletin.

www.answers.com/Q/What_measures_the_age_of_volcanic_rock

Finding the age of rocks based on the presence of naturally occurring long-lived radioactive isotopes of several elements in certain minerals and rocks.

www.quora.com/How-is-the-age-of-volcanic-rock-measured

Mostly, we know absolute age of igneous rock from radiometric dating. When an igneous rock is solidified from magma or lava, the radiometric ...

naturalhistory.si.edu/exhibits/backyard-dinosaurs/questions-answers.cfm?know=a24

The most important are Relative Dating, in which fossils and layers of rock are ... to measure the ages of volcanic layers in a stack of sedimentary rock, the entire ...

www.divediscover.whoi.edu/hottopics/volcano.html

In the early 1900's, scientists found a way to determine the real ages of rocks and ... Scientists can measure the argon-40 produced after eruption, and the ...

geology.utah.gov/map-pub/survey-notes/glad-you-asked/glad-you-asked-how-do-geologists-know-how-old-a-rock-is

Geologists generally know the age of a rock by determining the age of the group of ... each bed in a sequence of sedimentary rocks (or layered volcanic rocks) is ...

www.kidsdiscover.com/teacherresources/geologic-age-dating-explained

Sep 30, 2014 ... To determine the relative age of different rocks, geologists start with the ... several sedimentary layers, or maybe through another volcanic rock type. ... So geochronolgists just measure the ratio of the remaining parent atom to ...

pubs.usgs.gov/gip/geotime/radiometric.html

Jun 13, 2001 ... Although Boltwood's ages have since been revised, they did show ... of neodymium isotopes contained in a sample of igneous rock. ... of the various methods and techniques used to measure the age of Earth materials.

australianmuseum.net.au/radioactive-dating

Oct 6, 2009 ... This method is useful for igneous and metamorphic rocks, which cannot be ... of these isotopes within a rock or mineral can measure the age.