UTS 306K Exam 4

What evidence is there that can determine the existence of hot spots below the Earth's surface?

- A chain of volcanoes from oldest to youngest Ex: Hawaiian Islands= oceanic crust Yellowstone= continental crust

What evidence can be used to indicate the continents were once all together?

- Continent shapes - Fossils - Environments - Rock types & ages

How do you calculate the speed in which a plate is moving over a hotspot?

1. Find how much the plate has moved in kilometers: - measure distance b/t oldest and youngest volcano using a ruler in cm - use the map key to convert cm to km 2. Find how much time in years by subtracting the ages of the oldest and youngest volcanoes 3. Convert km from step 1 to cm: - km x 1000 = meters - m x 100 = cm 4. Use values calculated to determine speed: Speed = distance/time 5. State the speed you calculated above and in what direction the plate was moving: x cm/yr to the (direction)

How can you determine the direction a plate is moving over a hot spot?

1. Put your finger or pencil on the OLDEST volcano 2. Move the PAPER so your pencil is over the YOUNGEST volcano 3. The direction the PAPER moves is the direction the plate is moving over the hot spot

Why was the pancake batter a good model for what happens to the Earth's crust when heat is applied from below?

A great model for hotspots. The pancake model and Earth's hotspots both have stationary heat sources and the plate/tin for the pancake represents movement of plates over hotspots. The pancake also models how convection in the mantle creates bubbles which essentially represent how magma is released from the mantle and creates volcanoes.

Where does the coal form today?

Any place there is no oxygen, like swamp water. Conditions that prevent decomposition of plant material.

Where do the end products of weathering and erosion end up?

Bodies of water (streams, rivers, oceans, and beaches)

What is chemical sedimentary rock and how does it form?

Chemical sedimentary rock is made of fossils and/or composed of crystals of a single mineral. It has interlocking grains making it well cemented. It forms when the evaporation of water leaves behind minerals, like salt, forming chemical sedimentary rocks.

What is a clastic sedimentary rock and how does it form?

Clastic sedimentary rock is composed of fragments of pre-existing rock (usually clay and sand) along with limestone or silica which hold the rock together. They form when the components, including the water they are in, are heated by the core/mantle and sun. The water will eventually evaporate and clastic sedimentary rock will be what's left behind.

What is the most efficient heat flow mechanism w/in the Earth's CRUST?

Conduction because the crust is cold, brittle, and solid. The particles in the crust are more easily able to vibrate and transfer energy through neighbor to neighbor collisions since they are compact and close together.

What evidence is there to say that the continents are NOT floating in the oceans?

Continents float on the mantle. Water is less dense than the continents, because of this the continents would sink in the oceans. As for the mantle the continents are less dense since they are made of granite and basalt, therefore the continents float in the mantle.

What is the most efficient heat flow mechanism w/in the Earth's MANTLE?

Convection because the particles can move and are heated from below (the core). The mantle is a semi-solid and hot and can be deformed.

What type of geological phenomena define Earth's crustal plates?

Earthquakes and volcanoes

What is the name of the process of removing and transporting soil? What is the major transport mechanism of this process?

Erosion is the process of removing and transporting soil. The major transport mechanism of this process is rain/water. Others include wind and ice.

Which type of igenous rock makes up continental crust and oceanic crust?

Felsic rocks are found in the continental crust because they are made out of lighter materials making them lighter and less dense (ex: granite). Mafic rocks are found in the oceanic crust since they contain heavier elements making them more dense (ex: basalt).

How does gravity sliding contribute to plate tectonics?

Gravity sliding is caused by mantle convection. Mantle convection creates the slope for sliding. They work together to make the plates interact (diverge). The magma is the low friction source necessary as well as the ridges and mountains that create the slope for sliding.

Is gravity sliding more prevalent in oceanic or continental plate motion?

Gravity sliding is more prevalent in oceanic plate motion because new oceanic crust is formed at mid-ocean ridges where the weight of the ocean crust rests on a low-friction surface. A low-friction surface provided by the magma allows the plate to slide easily. Low-friction surfaces are not prevalent in continental crust, which is why gravity sliding is more prevalent in oceanic plate motions.

How does mantle convection contribute to plate tectonics?

Heat from the core heats up the lower layers of the mantle, making them less dense and more buoyant than cooler layers above. This heated, less dense magma rises to the surface as a convection cell. Partial melting occurs near the surface, injecting magma to form new crust. This magma coming from below pushes the crust in opposite directions, driving those plates away from one another (diverging).

What type of volcanoes and earthquakes are associated with convergent plate margins?

Large volcanoes and deep earthquakes. Pacific Northwest of the United States.

What are the three ways that the Earth's crustal plates can move with respect to one another?

Lava model: Converging- plates collide and the more dense plate fell into the lava Diverging- Plates are pulled apart Transform- Plates are side by side

What is the difference between the Earth's lithosphere and the asthenosphere?

Lithosphere: behaves like rock and is composed of Earth's solid crust and cool upper mantle Asthenosphere: Hot deep part of the mantle that behaves like a semi-solid/fluid over long periods of time.

Why are mafic rocks more dense than felsic rocks? Using elements.

Mafic rocks are more dense because they contain heavy elements, including iron. Iron is the heaviest metal and since mafic rocks contain it they are more dense than felsic rocks.

What are the three major forces driving the movement of the Earth's lithospheric plates.

Mantle Convection: occurs due to the heat of the Earth's core causing convection to occur within the semi-solid mantle. Thus creating new crust through thermal expansion. It is a DIVERGENT force. Gravity Sliding: occurs when a slope has a low friction surface. Both can be found on mid-ocean ridges so that allows newly made crust to slide down with ease. It is a DIVERGENT force. Subduction: occurs when crust sinks down when hitting a trench. As it sinks down, gravity will increase so it will sink in a relatively quick manner. It is a CONVERGENT force.

Describe the two types of weathering and their difference.

Mechanical weathering: physical breaking down of rocks WITHOUT changing composition. Chemical weathering: breaking down rocks by changing composition.

Which type of climatic conditions are preferred by mechanical weathering and chemical weathering?

Mechanical- Cold temperatures, and a medium amount of water. Cold temperatures need to be present so that the water will freeze. Chemical- Hot temperatures, and lots of water. High rainfall and temperatures need to be present because the rain allows for acid to break down the rocks, and the high temperatures allow for the chemical reaction to occur quickly.

What type of volcanoes and earthquakes are associated with divergent oceanic plate margins?

No volcanoes: lava flows occur at mid-ocean ridges. Shallow earthquakes. Mid-Atlantic ridge.

Does subduction/slab pull affect continental lithosphere?

No, because subduction only occurs in oceanic crust, which is more dense than continental crust. Continental plates are so thick that they will not be dense enough and will not be subductive (beach ball).

Are continental boundaries the same as plate boundaries?

No, there are plates that contain both oceanic and continental crust.

Are areas of high heat flow generally located in ocean basins or beneath continental land masses?

Ocean basins. High amounts of thermal expansion happens in the ocean basins. This is how thermal mountains are created.

Why do oceanic plates move faster than continental plates?

Oceanic crust has three forces affecting their movement: Mantle convection, gravity sliding, and slab pull/subduction. The oceanic crust are thinner and more dense so it is more easily affected by these three forces. Continental crust is only affected by mantle convection. Since oceanic crust has three forces acting on it and continental crust only has one, oceanic crust moves faster.

What is a heat source deep within the Earth?

Radioactive decay from the core

Why is the interior of the Earth still hot after many years of geological time?

The crust acts as an insulator for the heat in the Earth. The natural radioactive breakdown of unstable elements continually occurring in the core is also responsible.

What is an end product of both mechanical and chemical weathering?

The end products would be clay minerals and sand. Soil.

Why does liquid magma have a tendency to rise toward the surface of the Earth?

The liquid magma will rise towards the surface of the Earth because it is less dense.

How does the lithosphere thicken over time?

The semi-solid mantle is heated from the core because it is undergoing convection, as it rises, it makes contact with the lithosphere and freezes and attaches to the crust.

How can the size of an igneous rock's mineral crystals tell us how long it took to cool relative to other igneous rocks?

The smaller the crystal, the less time it had to cool. Rapid cooling time. The bigger the crystal, the more time it had to cool. Slow cooling time.

What evidence indicates convergent plate boundaries?

Volcanoes, plates moving under one another.

Why do you think that shells of most sea animals are made of limestone?

Warm water is saturated with limestone, there was an abundant amount, so animals started to use it like a house. It's just like how we use wood for houses. In the warm water, the CO2 evaporates and leaves the limestone, which builds up and creates thick deposits over time. Reefs/shellfish/corals live in this warm water.

Is young oceanic lithosphere buoyant with respect to the semi-solid mantle asthenosphere? What about old (100 million years) oceanic lithosphere?

Young lithosphere: Yes, since the young lithosphere is warmer there is more space between the particles making it less dense. It also has not gone through lithospheric thickening. Old lithosphere: No, since it is older it has cooled causing there to be less space between particles making it more dense.

What evidence indicates divergent boundaries?

Young oceanic crust being formed.

Are areas of high heat flow associated with young or old rock?

Young rock. This is because young rock is still hot since it is newly formed, it has not gotten the chance to completely cool in comparison to older rock.