Liza concludes that a rock formed before a nearby lava flow, without assigning an age in years. Which approach did she use?

Which layer in this undisturbed sequence formed first?

Which principle helps geologists infer that these inclined sedimentary beds were disturbed after deposition?

Which sequence lists layer C, intrusion E, and layer D from earliest to latest?

Which layer was deposited after movement along fault F?

Which formed first: the angular rock fragments enclosed in layer B, or layer B itself?

What type of boundary is marked U?

An eroded gneiss surface is covered by sandstone. What type of gap in the rock record does this contact represent?

Which contact is a disconformity?

Matching fossil assemblages occur in two distant sedimentary layers. What can this evidence help geologists determine?

A closed mineral initially had no daughter isotope. It now has 30 parent atoms and 90 daughter atoms produced by decay. How many half-lives have elapsed?

Which interval defines an isotope's half-life?

What is the half-life of the isotope represented by this curve?

What percentage of the original radioactive parent atoms remains after three half-lives?

A closed sample retains 25% of its original parent isotope after 5,000 years. What is the isotope's half-life?

Which charcoal sample from a Philippine site falls within the usual age range of carbon-14 dating?

A sandstone contains mineral grains carried from other rocks. What do radiometric ages of these unaltered grains usually record?

An undisturbed sedimentary bed lies above ash dated to 12 million years and below ash dated to 8 million years. Which age could the bed have?

Which method estimates the age of wood by matching annual growth patterns to a reference record?

What does one complete light-and-dark sediment pair in a lake varve usually represent?