Lecture 1 - Key Concepts Flashcards
What methods can be used to study the interior of the Earth?
Magnetism
Inertia
Lower frequency seismic waves (main method).
What are P waves?
Primary waves are longitudinal waves.
They can travel through all mediums.
What are S waves?
Secondary waves are transverse waves.
They cannot travel through liquids.
How do geologists sort events in Earth’s history into a sequence of events?
By using numerical (absolute) ages or relative ages.
What is stratigraphy?
The study of the sequence of events in Earth’s history.
What information can each stratum provide?
The conditions of the Earth’s surface in the past.
What is uniformitarianism?
The idea that ‘the present is the key to the past’.
It was proposed by James Hutton.
What are two laws of stratigraphy?
The Law of Original Horizontality.
The Principle of Stratigraphic Superposition.
What is the law of original horizontality?
Water laid sediments are deposited in strata that are horizontal or nearly horizontal.
What is the principle of stratigraphic superposition?
Sedimentary strata are deposited from bottom to top.
This means that the youngest sediments are deposited on top of the older sedimentary rocks.
What is an unconformity?
A substantial break or gap in a stratigraphic sequence.
What are the three kinds of unconformity?
Angular unconformity.
Disconformity.
Nonconformity.
What is an angular unconformity?
Where older strata is deformed and then cut off by erosion. Younger layers are then deposited across them.
What is an example where there is an angular unconformity?
Siccar Point.
What is a disconformity?
An irregular erosion surface between parallel layers of strata.
This is difficult to identify and can only be seen by studying fossils.
What is a nonconformity?
Where younger strata overlie igneous or metamorphic rock.
What is the rock stratigraphic record?
Areas where there are distinctive strata that differ from those above/below it.
For example, Navaho Sandstone in the Zion National Park.
What is the time stratigraphic record?
Classification based on rocks formed within a specific time interval.
What is the primary unit of geological time?
A period.
What is a period?
The time during which a geological system accumulated.
Is the geological record complete?
No, there may be gaps in an area. These gaps can be bridged by piecing together pieces of strata from nearby geographic areas.
What is correlation?
The determination of equivalence in time-stratigraphic or rock-stratigraphic units of the succession of strata found in two or more different places.
What can be used to aid correlation?
Volcanic ash layers.
Biostratigraphy (using fossils).
What is the geological column?
A composite column that contains the succession of strata in chronological order.
