Questions:Modeling of Earth's Interior

Base your answers to questions 1 through 6 on the information below and on your knowledge of Earth and Space Sciences.

Modeling Earth's Interior

While other planets experience tectonic deformation in the form of volcanic activity, Earth is the only planet currently known to exhibit active plate tectonics involving multiple plates. To gain a better understanding of Earth’s interior, scientists have developed models using seismic waves, rock samples, and laboratory experiments. These models assist scientists in the visualization of Earth’s complex interior and crustal dynamics.

Conditions within Earth’s interior cause different substances to be found at different depths. The table below shows regions within Earth’s interior where some substances are found.

Region (depths)	Substances
inner core (6371-5150 km)	solid, stable iron
outer core (5150-2891 km)	liquid iron
lower mantle (2891-670 km)	magnesium and iron-bearing silicon
transition zone (670-410 km)	structures with both SiO₄ and SiO₆ groups (e.g. majorite garnet)
upper mantle (410-40 km)	olivine, pyroxene, garnet, spinel
crust (average depth 40 km)	feldspar, quartz

The graph below shows some information about the velocity of seismic waves as the waves travel through Earth's Interior

1. Which row in the table below correctly describes the substance(s) found in Earth's interior and the characteristic of that interior layer of Earth?

Row	Substance(s) in Earth's Interior	Characteristics of Earth's Interior
A	liquid iron	found in a layer where compressional velocity is greatest in Earth's interior
B	solid, stable iron	found in a layer where compressional wave velocity is approximately 11.2 km/sec
C	pyroxene and quartz	found only at a depth of 500 kilometers
D	magniesium silicates	found in a layer where shear wave velocity is greater than compressional wave velocity

Row A
Row B
Row C
Row D

2. Seismic wave information was used by scientists to infer the depth of Earth's interior layers and the states of matter found in these layers. For each piece of evidence (A and B) below, place an X into the appropriate box to indicate the characteristic that can be inferred and explain how this evidence changes and is used to determine this characteristic. [1]

Evidence from Graph		Characteristic's of Earth's Interior Layers
	Change in Density	Change in Magnetism
A Sudden change in velocity
Explanation 1: ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________
	Depth	State of Matter
B Presence of certain types of seismic waves
Explanation 2: ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________

Techtonic processes are responsible for the formation of many types of rocks and minerals found on Earth. The model below shows some information about different tectonic plate interactions found on and below Earth's surface.

All models of Earth's interior depend on indirect evidence. These models predict the sources of heat in Earth's interior. The substances found in the different layers of Earth's interior determine the possible source of heat in each layer. The core contains elements that "like to be with iron", but the mantle and crust contain "rock-loving" elements. These elements are the source of rock-forming minerals of the Earth's crust. Uranium, thorium, and potassium are unstable isotopes that are examples of these "rock-loving" elements.

3. Which statement correctly describes a source of heat within Earth's interior?

Radioactive isotopes in Earth's interior decay in the mantle and crust, further driving convection currents that cycle materials.
Radioactive activity in the mantle and crust helps to cycle materials into Earth's inner core and asthenosphere.
Radioactive elements in Earth's interior decay, cycling materials in convection currents only within Earth's crust.
Radioactive isotopes in Earth's interior decay, cycling materials in convection currents formed in the mantle and asthenosphere.

The model below represents processes involved in rock formation. Tectonic processes labeled A and B are missing.

4. Using evidence from the Earth's Surface and Interior Model, complete the Rock Cycle Model by identifying one tectonic plate interaction that is responsible for the formation of each rock type indicated. [1]

Tectonic interaction A: ____________________________________________________________________

Tectonic interaction B: ____________________________________________________________________

Certain magnetic minerals in rocks can record the direction and intensity of Earth's magnetic field at the time they are formed. The direction of Earth's magnetic field has reversed several times during Earth's history. These reversals are recorded in the bedrock of the ocean floor.
The model below shows some information about the age and magnetic polarity of ocean floor bedrock along the Juan de Fuca ridge system.

5. Which statement correctly compares locations on the Juan de Fuca Ridge Model

The basalt at location A is older than the basalt at location B
A greater amount of outward flow of energy from Earth's interior occurs at location A than at location B
The magnetic polarity of basalt at location A is the same as the magnetic polarity at location B
The motion of the tectonic plate is from location B to location A

6. Describe how the pattern of magnetic field reversal of ocean floor basalt shown in the rocks on either side of the Juan de Fuca Ridge is evidence for convection currents in the mantle. [1]

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