1.3 C: Geology = the Changing Earth 1.3 Strange Rocks Flashcards
What is the law of superposition?
A law stating that higher strata in a sequence of rock layers are younger than lower strata
This law helps geologists determine the relative ages of rock layers.
What is relative dating?
The process of placing rocks and geological structures in the correct chronological order
Relative dating allows geologists to determine which rock layers are older or younger.
Define stratigraphic sequence.
A sequence of rocks that provides a chronological record of a region’s geological history
The stratigraphic sequence is crucial for understanding the geological past.
What is an intrusion in geology?
A body of rock that forms from the invasion of magma into a pre-existing rock formation
Intrusions are younger than the surrounding rock because they form after the existing rock layers.
Fill in the blank: The process of determining which rock layers are older and which are younger is called _______.
relative dating
True or False: The clothes at the bottom of a laundry basket are the youngest.
False
The clothes at the bottom are the oldest because they were deposited first.
What is the significance of the law of superposition in geology?
It provides a way for geologists to keep track of the order in which rock layers formed
This law is foundational for understanding geological history.
List two key concepts related to the study of rock layers.
- Law of superposition
- Relative dating
Fill in the blank: The pattern of rocks in strata is called _______.
stratigraphic sequence
What happens when a large underground body of magma invades cracks in sedimentary rock?
It forms an intrusion, which is younger than the surrounding rock
This process can disrupt the normal order of rock layers.
What is the process by which rivers transport materials to the ocean?
Sediment transport
What type of rock forms on the ocean floor and contains fossils?
Sedimentary rock
Fill in the blank: Younger stratum contains _______ with more recent fossils.
fossils
What happens to sedimentary rocks as sea levels change?
They are pushed upward and exposed
True or False: Older strata contain younger fossils.
False
What is revealed through erosion by rivers?
Older strata
Over time, what accumulates on top of older strata?
Additional strata containing fossils from each time period
Fill in the blank: The process of sedimentary rock formation involves the accumulation of _______.
sediment
What is the relationship between strata and fossils in geological time?
Younger strata have more recent fossils, while older strata have older fossils
What geological feature is formed by the accumulation of sediments over time?
Strata
What is the principle of relative dating used for?
To put items in chronological order based on their layers
Relative dating helps in establishing the sequence of events but does not provide exact dates.
What does relative dating reveal about sediment layers?
Younger layers are deposited on top of older layers
This principle allows geologists to assign relative dates to fossils and events.
What is the main limitation of relative dating?
It does not reveal the absolute age of events or fossils
Absolute age provides a specific number of years since an event occurred.
True or False: Relative dating can determine the exact number of days since an item was placed in a laundry basket.
False
Relative dating can only determine the sequence, not the exact timing.
Fill in the blank: The principle of relative dating allows geologists to assign _______ to fossils and events.
relative dates
Relative dates indicate the sequence of events without specifying exact ages.
What law did early geologists use to rank strata and fossils in chronological order?
Steno’s law of superposition
What was a major limitation in early geology before William Smith’s contributions?
A unified history of Earth’s Crust for entire regions or the entire planet
Who was William Smith and what was his profession?
An English surveyor
What was one of William Smith’s significant jobs as a surveyor?
Acting as a surveyor for a canal project
Why were surveyors important during excavation projects?
Digger had to know what types of rocks to expect
What did William Smith carefully examine at many dig sites?
The rock strata
What significant hypothesis did William Smith develop from his observations?
Certain distinctive fossils kept re-appearing at each surveyed location
Fill in the blank: William Smith traveled all over England as a _______.
[surveyor]
True or False: William Smith’s observations were instrumental in constructing a unified geological history.
True
What is an index fossil?
A fossil used to determine the relative age of a layer in a stratigraphic sequence or to match stratigraphic sequences from different locations
Index fossils provide a way to correlate the ages of rocks from different locations based on the presence of specific fossils.
How do index fossils establish age correlation?
If a distinctive fossil existed only for a limited period of time, then rocks containing that fossil must correspond closely in age with other rocks that contain that same fossil
This correlation allows geologists to date rock layers and understand their temporal relationships.
Why are certain fossils referred to as distinctive fossils?
They existed only for a limited period of time
Distinctive fossils serve as markers for specific geological time frames.
Fill in the blank: Index fossils are like an _______ to establish a common time of origin for widely dispersed rock layers.
index
True or False: Index fossils can be used to match stratigraphic sequences from different locations.
True
What is the main purpose of using index fossils in geology?
To determine the relative age of rock layers and correlate them across different locations
This helps in constructing a more comprehensive geological history.
Who was the scientist known for creating the first complete geological map of England?
William Smith
Smith published his map in 1815.
What method did Smith use to match different rock strata from various locations?
Index fossils
Index fossils are used to correlate the ages of rock layers.
In what year did Smith publish his geological map?
1815
This was considered his greatest achievement as a scientist.
At what age did Smith finally receive a major award for his contributions to geology?
62
This recognition came 16 years after the publication of his map.
True or False: Smith’s contributions were immediately recognized after the publication of his geological map.
False
His work was largely ignored initially.
What was a significant challenge faced by Smith regarding the recognition of his work?
His humble beginnings and education
These factors contributed to the initial oversight of his contributions.
Fill in the blank: Smith’s geological map was published _______.
[1815]
What is an index fossil?
A useful index fossil appears only briefly in the geological record, has a wide geographical distribution, and is easily recognizable.
Index fossils are crucial for dating and correlating the strata in which they are found.
What did geologists use index fossils for in the nineteenth century?
To assemble a generalized relative time scale for all of Earth.
This was significant for understanding geological history before the advent of radiometric dating.
What is the Geological Time Scale?
An idealized sequence that generalizes Earth’s entire history, divided into four major eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic.
The scale is based on fossil records and geological events.
What are the four major eras of the Geological Time Scale?
- Precambrian
- Paleozoic
- Mesozoic
- Cenozoic
Each era is characterized by significant geological and biological events.
What marks the boundary between each era in the Geological Time Scale?
A massive disappearance of fossils and an unexplained appearance of new fossils.
These changes indicate major shifts in Earth’s biological and geological history.
What smaller divisions are used within each era of the Geological Time Scale?
Periods, and in some cases, periods are broken down into epochs.
This hierarchical structure allows for a more detailed understanding of Earth’s history.
True or False: Geologists have fully agreed upon the details of the Geological Time Scale.
False
Geologists continue to debate and refine details of this time scale as new evidence emerges.
Fill in the blank: The Geological Time Scale is divided into four major eras: Precambrian, Paleozoic, ________, and Cenozoic.
[Mesozoic]
What is the significance of an ideal stratigraphic column?
It generalizes Earth’s entire history by assembling sequences from all over the world.
This allows for a comprehensive understanding of geological time despite the incomplete nature of the fossil record.
What is the time frame of the Quaternary period?
1.7 million years ago to present.
The Quaternary is the most recent geological period and includes the current Holocene epoch.
What does the term ‘resistance to erosion’ refer to in geology?
The ability of rocks to withstand weathering and erosion processes.
This characteristic influences the landscape and geological formations.
