Rock Cycle & Geology
This principle states that the geologic processes happening today also happened in the past.
What is uniformitarianism?
According to this law, in horizontal sedimentary layers, the oldest layer is at the bottom.
What is the law of superposition?
The process in which atoms of one element break down to form atoms of another.
What is radioactive decay?
Earth’s outer layer is broken into these pieces.
What are plates?
The earliest life forms found in 3.5‑billion‑year‑old rocks.
What are single‑celled organisms similar to bacteria?
These are the three main types of rock.
What are igneous, sedimentary, and metamorphic rocks?
These features—such as faults, intrusions, and extrusions—help determine relative age.
What are geologic features used for relative dating?
The time it takes for half of a radioactive element to decay.
What is a half-life?
The theory explaining that Earth’s landmasses move over time.
What is the theory of plate tectonics?
The timeline showing the span of Earth’s history.
What is the geologic time scale?
This type of rock forms when melted material cools and hardens.
What is igneous rock?
These fossils help geologists match rock layers of the same age in different places.
What are index fossils?
This method determines the absolute age of rocks.
What is radioactive dating?
The idea that continents slowly moved across Earth’s surface.
What is continental drift?
The era that began with many new organisms evolving.
What is the Paleozoic Era?
This type of rock forms from particles pressed and cemented together.
What is sedimentary rock?
A gap in the geologic record caused by erosion.
What is an unconformity?
Radioactive dating shows Earth is approximately this old.
What is 4.6 billion years old?
Plate movement explains why fossils of this dinosaur appear on several continents.
What is Brachiosaurus?
A mass extinction ended this era about 65 million years ago.
What is the Mesozoic Era?
This type of rock forms when existing rock is changed by heat or pressure.
What is metamorphic rock?
Pieces of rock found inside another rock layer that must be older than the layer containing them.
What are inclusions?
The type of age determined by comparing radioactive decay amounts.
What is absolute age?
The movement of plates changed landmass locations and affected where these are found.
What are organisms, past and present?
During this era, mammals evolved to live in many environments.
What is the Cenozoic Era?