Ameteorite is determined to be 4.5 billion years old. it now has 78 atoms of lead-206. assuming no loss of daughter isotopes, how many atoms of uranium-238 did the meteorite have to begin with? the half-life of uranium-238 is 4.5 billion years. a) 156 b) 312 c) 78 d) 238

Which statement is true regarding weathering in dry environments? a) chemical weathering is absent because of a lack of humidity. b) physical weathering is usually more evident than chemical weathering. c) it is impossible to identify the type of weathering that has occurred. d) physical weathering does not play a significant role in dry environments.