Earth's History - Relative Dating

How do index fossils help scientists? - They aid in the study of ranges of different organisms. - They advance understanding of the origin of life on Earth. - They aid in comparison of rock layers at distant locations. - They advance understanding of rock type at the time the organism lived.

They aid in comparison of rock layers at distant locations.

A geologist finds some tilted sedimentary rock layers. Which conclusion can the geologist draw by looking at the rock layers? - Their absolute age is 600 million years. - They were tilted before they were deposited. - They were originally deposited horizontally. - The youngest layer was originally deposited as the bottom layer.

They were originally deposited horizontally.

A geologist finds four layers of sedimentary rock. She determines that no geologic events have shifted the layers. She labels the layers A, B, C, and D from the top to the bottom. Which statement about these layers is accurate? A is older than B. B is older than C. C is younger than A. B is younger than D.

B is younger than D.

Which event is most likely if an index fossil is found in a layer at location 1, but the layer and index fossil are not found at location 2 nearby, which is known to be the same relative age? - The layer at location 2 is too old to contain fossils. - The locations were too close together. - The organism did not exist at location 2. - The layers at location 2 formed much earlier than those at location 1.

The organism did not exist at location 2.

Which statement about how geologists study the ages of rock layers is true? - The law of superposition means that older rocks are on top. - Geologists can find the exact age of a rock by looking at its relative position. - The principle of original horizontality provides the basis for the law of superposition. - Relative age can be determined by using the concept of unconformity.

The principle of original horizontality provides the basis for the law of superposition.

Which phrase describes faults? cause gaps in the geologic record cause rocks to break and move are older than surrounding rocks are igneous rocks that form beneath Earth's surface

cause rocks to break and move

Which feature causes a gap in the geologic record? extrusion fault intrusion erosion

erosion

Which feature forms at Earth's surface from the cooling of lava? extrusion fault intrusion unconformity

extrusion

Which phrase describes the absolute age of a rock? does not provide an exact age is the number of years since it formed is the age compared to other rocks around it indicates whether it is younger or older than the rocks above it

is the number of years since it formed

Geologists use tools other than the law of superposition to help them with relative dating. Which statements describe those tools? Check all that apply. - An unconformity is created when lava pours out on Earth's surface. - Faults are the result of volcanic activity. - Intrusions and extrusions are sedimentary formations. - Cross-cutting features are always younger than the surrounding rock. - When material erodes before sediment is deposited on it, a geologic gap results.

- Cross-cutting features are always younger than the surrounding rock. - When material erodes before sediment is deposited on it, a geologic gap results.

Which characteristic is shared by extrusions, intrusions, and faults? All are cracks. All are igneous rocks. All cause gaps in the geologic record. All are younger than surrounding rocks.

All are younger than surrounding rocks.

In which situation is the principle of cross-cutting relationships useful in determining relative age? - A fault breaks through sedimentary layers. - Fossils of two different species are found in different rock layers. - Sedimentary layers form over millions of years in a lake bottom. - Lava flows form on top of one another from several eruptions over time.

A fault breaks through sedimentary layers.

Which statement describes the law of superposition? - Sedimentary rocks were originally in horizontal layers. - In horizontal rock layers, each layer is younger than the one below it. - Rock layers must be in existence before something can happen to them. - Rocks that are not in horizontal layers were shifted by some geologic event.

In horizontal rock layers, each layer is younger than the one below it.

A scientist finds a fossil that she thinks might make a good index fossil. Which characteristic does this fossil most likely have? - It is the remains of an organism still found alive today. - It is the remains of an organism that is found in abundance nearby. - It is the only fossil for this type of organism that has ever been found. - It is the remains of an organism that lived in a narrow geographic area.

It is the remains of an organism that is found in abundance nearby.

Which statement explains one reason why unconformities occur? - Rocks along a fault break and move. - Igneous rock forms at Earth's surface. - No sediment is deposited over a long time. - Igneous rock forms between sedimentary layers.

No sediment is deposited over a long time.

Which phrase describes organisms that formed index fossils? are extinct had soft parts were generally large lived in a narrow geographic area

are extinct

Which is the first step that geologists must do to compare rock layers at distant locations? - find the absolute age of rocks at both locations - compare a layer at one location to layers at other locations - identify index fossils in one or more layers at one location - collect fossils from different locations to study the organisms' lifestyles

identify index fossils in one or more layers at one location

Which correctly lists three different geologic features that help scientists determine the relative ages of rocks by their positions? - magma, erosion, and intrusions - erosion, magma, and cross-cutting relationships - intrusions, index fossils, and magma - index fossils, intrusions, and cross-cutting relationships

index fossils, intrusions, and cross-cutting relationships

Which phrase describes the relative age of a rock? - uses the law of superposition to determine which rock is older or younger - can determine the age based on location of a rock within the same layer - requires only one rock to determine the age - can provide the exact age of a rock

uses the law of superposition to determine which rock is older or younger