Geology Principles and Key Terms

Questions and Answers

Who proposed the principle of horizontality?

Nicholas Steno

What does the principle of cross-cutting state?

Igneous intrusion is always younger than the rock it cuts across.

What is an angular unconformity?

Older, deformed rock layers that are tilted and usually slightly eroded before the deposit of new rock layers.

What is the Grand Canyon known for?

Evidence of millions of years of rock forming processes. Signup and view all the answers

What are geologic events characterized by?

Original sediments were deposited horizontally, then tectonic forces deformed the rock. Signup and view all the answers

What is a dike?

A sheet of rock that was formed in a fracture in a pre-existing rock body. Signup and view all the answers

What are swarm dikes?

Multiple formations located in the Northwest Territories, Canada. Signup and view all the answers

What are ring dikes?

A type of dike that forms around volcanic necks or feeder vents. Signup and view all the answers

What are sills?

A tabular sheet intrusion that has intruded between older layers of sedimentary rock. Signup and view all the answers

What does the Law of Superposition state?

A given bed must be older than any bed on top of it. Signup and view all the answers

What is stratigraphy?

The science of strata and the characteristics of layered rocks. Signup and view all the answers

Study Notes

Principles and Key Terms in Geology

Nicholas Steno: Danish geologist known for establishing the principle of original horizontality, stating that sediment layers are deposited horizontally due to gravity.
Cross-cutting Relationships: This principle asserts that an igneous intrusion must be younger than the rock it penetrates, illustrated by examples like the igneous intrusion cutting through metamorphic rock in Death Valley, California.
Angular Unconformity: Found in the Grand Canyon, it describes older rock layers that have been tilted and partially eroded before subsequent layers are deposited, indicating a significant geological history.
Grand Canyon: A major geological site in Arizona showcasing millions of years of sedimentary processes and stratification, critical for understanding Earth’s geological history.
Geologic Events: The geological timeline includes horizontal deposition of sediments, tectonic forces tilting the rocks, erosion, and a subsequent period of sediment deposition leading to angular unconformities.
Dikes: Formed by magma intruding into pre-existing rock, dikes are sheet-like formations that crystallize within fractures, altering the surrounding geological landscape.
Swarm Dikes: A notable example is the Mackenzie dike swarm in Canada’s Northwest Territories, consisting of multiple dike formations indicative of extensive volcanic activity.
Ring Dikes: These structures form around volcanic necks or feeder vents, often associated with the internal processes of volcanic cones reflecting the movement of magma.
Sills: Tabular intrusions that occur between layers of older sedimentary rock or volcanic deposits, providing insights into the timeline of geological events and magma movement.
Law of Superposition: This principle states that in an undeformed sequence of sedimentary rocks, older layers are located below younger layers, allowing geologists to determine relative ages.
Stratigraphy: The branch of geology that involves studying rock layers (strata), focusing on their characteristics and the temporal relationships among them, crucial for understanding Earth's history.

Description

Explore the fundamental principles of geology, including Steno's original horizontality, cross-cutting relationships, and angular unconformities. This quiz covers key geological terms and examples, particularly focusing on the Grand Canyon's geological history. Test your knowledge of how these principles shape our understanding of Earth's processes.