ASTRO 115 Lecture Notes - Lecture 4: Radioactive Decay, Radionuclide, Mass Number
Document Summary
Over longer time scales, life and geology deeply intertwined: three aspects: Volcanism: releases gases trapped in earth"s interior, creates chemical environments that helped lead to origin of life on our planet. Plate tectonics: movement and recycling of rock between surface and interior: recycles seafloor crust, continually add to continental crust, responsible for long-term climate stability. Basalt: dark dense, produced by undersea volcanoes, composed of silicate minerals. Alpha decay: large atomic nucleus ejects he nucleus (2 protons and 2 neutrons: remaining daughter nucleus has lower atomic mass than parent, e. g. U-238 decays by ejecting he nucleus, leaving th-234 as daughter, goes through 8 chain of decay, until u-238 changes to pb-206, which is stable. Radioactive decay always occurs at specific measurable rate. Carbon-14: carbon only useful or dating objects less than 50,000 years old. 2 log10( current amount original amount log10( 1. 2 groundwater gradually replace organic material: fossil left by the activity of an organism while it was alive.
