Final answer:
The age of the rock can be determined using radiometric dating methods.
Step-by-step explanation:
The age of the rock your friend picked up in Iceland at the mid-oceanic ridge compared to a rock in Maryland can be determined using geological dating methods. One commonly used method is radiometric dating, which involves measuring the ratio of isotopes in a rock sample to determine its age. For example, the rubidium-strontium dating method can be used to determine the age of rocks by analyzing the decay of radioactive rubidium isotopes to stable strontium isotopes. By comparing the ages of rocks from different locations, geologists can gain insights into the relative ages of rocks and the geological processes that have shaped them.