Here's a breakdown:

* Geologists study the Earth's physical structure, composition, and history. They analyze rocks, minerals, fossils, and landforms to understand the processes that have shaped our planet.

* Petrologists specialize in the study of rocks, including their formation, composition, and properties.

* Mineralogists focus on the study of minerals, their identification, and their properties.

* Geomorphologists study landforms, their formation, and evolution.

* Paleontologists focus on fossils and the history of life on Earth.

* Seismologists study earthquakes and seismic waves.

* Volcanologists specialize in the study of volcanoes and volcanic activity.

Beyond these specific areas, a geologist may work in:

* Exploration for natural resources (oil, gas, minerals)

* Environmental assessment and remediation

* Engineering geology (assessing geological conditions for construction projects)

* Teaching and research

* Government agencies (monitoring geological hazards, managing natural resources)

So, while "geologist" is the most common term, there are many specialized areas within this field, each with its own focus and expertise.