Earth Systems Geology Test

What principle states that sedimentary rock layers are formed in horizontal layers?

The Principle of Original Horizontality.

According to the Principle of Superposition, which rock layer is the oldest?

The lowest rock layer is the oldest.

If a fault cuts through several rock layers, which occurred first, the faulting or the formation of the rock layers?

The rock layers formed first, and the faulting occurred afterward (Principle of Cross-Cutting Relationships).

What is an unconformity and what does it indicate about the geologic record?

An unconformity is a gap in the geologic record, indicating erosion or non-deposition of layers.

How can volcanic ash layers help correlate rock layers across different locations?

Volcanic ash layers are widespread and can provide precise time markers across regions.

What is an index fossil and what makes it useful for dating rock layers?

An index fossil is a fossil of a species that existed for a short time and is found in many locations. It helps date the rock layers in which it is found.

What does the presence of fossils in sedimentary rocks tell us about Earth’s past environments?

Fossils provide clues about past climates, ecosystems, and the types of organisms that lived in different eras.

How do fossils help scientists understand the evolution of life on Earth?

Fossils show how life-forms have changed over time and help trace evolutionary patterns.

Which type of organisms are commonly used as index fossils?

Marine organisms such as ammonoids and trilobites are often used due to their wide distribution and rapid evolution.

Why are most of the organisms that once lived on Earth now extinct?

The fossil record shows that many species have gone extinct due to environmental changes, competition, or other factors.

What causes contact metamorphism and what type of rock is typically formed?

Contact metamorphism occurs when heat from an igneous intrusion alters surrounding rock, forming rocks like hornfels.

What type of geologic feature is created by the interaction of tectonic plates?

Landforms such as mountain ranges, valleys, and volcanoes are created by tectonic interactions.

How have plate tectonics influenced the Earth’s climate over time?

Plate tectonics have changed Earth's geography, influencing ocean currents, atmospheric patterns, and climate.

How can volcanic eruptions affect Earth’s atmosphere?

Volcanic eruptions release gases like carbon dioxide and water vapor, contributing to the formation of Earth’s early atmosphere.

What major event marks the beginning of the Adirondack Mountains' uplift?

The Adirondack Mountains began uplifting during the Cretaceous period.

What gases were present in Earth’s early atmosphere?

Water vapor, carbon dioxide, and nitrogen were the primary gases in Earth’s early atmosphere.

When did oxygen-producing organisms first evolve?

Oxygen-producing organisms evolved later, significantly increasing the oxygen content in the atmosphere.

What does fossil evidence reveal about the history of life on Earth?

Fossils show that many life forms have existed and evolved, with many now extinct.

How did Earth’s oceans form, and what evidence supports this?

Earth’s oceans formed through precipitation over millions of years, with marine sedimentary rocks dating back over four billion years.

Why is human existence considered brief in geological terms?

Humans have only existed for less than 1% of Earth’s geologic history.

What is radioactive decay, and how is it used to date rocks?

Radioactive decay is the process where unstable isotopes decay into stable ones. The rate of decay (half-life) allows scientists to determine the absolute age of rocks.

Why is Carbon-14 used to date recent fossils?

Carbon-14 has a short half-life, making it ideal for dating fossils less than 50,000 years old.

How does Uranium-238 help date very old rocks?

Uranium-238 has a long half-life, allowing it to be used for dating rocks that are billions of years old.

Why can’t Carbon-14 be used to date very old rock layers?

Carbon-14 decays too quickly to date ancient rocks that are millions of years old.

What is the half-life of Potassium-40, and how is it used in dating?

Potassium-40 has a long half-life, making it useful for dating ancient rocks and fossils, typically over a million years old.

Original Horizontality

A principle stating that layers of sediment are originally deposited in horizontal layers. Over time, they might tilt or fold due to movements in the Earth's crust.

Superposition

In undisturbed rock layers, the oldest layer is at the bottom, and the youngest is at the top.

Cross-Cutting Relationships

A rock layer or fault that cuts through other layers is younger than the layers it cuts through.

Contact Metamorphism

When hot magma intrudes into surrounding rocks, the heat causes changes (metamorphism) in those rocks at the contact point.

Unconformities

Gaps in the rock record where layers are missing due to erosion or a lack of deposition.