Coal is formed when heat and pressure alter deposits of ancient ________.

Magnetostratigraphy takes advantage of the fact that Earth’s magnetic field ________.

Medium- and deep-focus earthquakes occur along only ________.

Volcanoes have provided some positive benefits to humankind and life in general over geologic time. Which of the following is NOT true about volcanoes?

How is the half-life of a radioactive parent isotope defined?

Relative ages expressed on the geologic time scale primarily resulted from the study of ________.

Most of the hydrocarbons within oil and natural gas are derived from the breakdown of organic matter from once-living ________.

Volcanic bombs are ________.

Which of the following is NOT a possible consequence of an increased greenhouse effect?

Thunderstorms are associated with ______ clouds.