Geography test 3

Geography test 3 - Geol test 3 first section of notes •...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Geol test 3 March 12, 2007 ????? first section of notes • Now use the methods of “calibrate” geological time scale based on sedimentary rocks only, and RADIOMETRIV AGES ONLY POSSIBLE FOR IGNEOUS ROCKS. • SEDIMENTARY ROCKS CANNOT BE RADIOMETRICALLY DATES • For sedimentary rock, :age: is when sediment laid down (fossil enclosed) detritial sedimentary rocks contain broken solid grains • Best method- date ash beds found mixed with sedimentary rocks. These follow the principal of superposition. o Rocks above ashbed are younger. o Rocks below ash bed are older • Important examples of dating o U-PB METHOD Age of the earth- 4500m.y.- based on dating of meteriorites formed at the same time as the earth Explotion of life forms at base of palezioc occurred ~55o m.y. ago Faunal extinction event at palezioc-mezezioc boundry occurred ~22o m.y. ago o K-AR METHOD Funaul extinction event at mezezoic- cenozioc boundry occurred 65 m.y. ago Man like creatures first appeared in east Africa ~5 n.y. ago...
View Full Document

{[ snackBarMessage ]}

Page1 / 3

Geography test 3 - Geol test 3 first section of notes •...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online