Lab 1 – Plate Tectonics

Lab 1 – Plate Tectonics

GEO101C – Earth Science

Colorado State University Global

TOPOGRAPHIC PATTERNS

Are mountains randomly distributed on the continents, or do they tend to occur in particular patterns (clusters, linear chains, arcs, etc.)?

Patterns.

Find Mt. Everest, the highest point on earth. Zoom in enough to see the summit, then pan your cursor around to locate the highest point (elevations show up in the status bar at the bottom, as long as View/Status Bar is selected). The elevation of Mt. Everest is how many meters?

Approximately 9000 meters.

In the space below, complete the topographic profile of the Atlantic Ocean floor between South America and Africa. Take a digital photograph of your sketch to include in your lab report.

Scan around to see the ocean ridges in the Indian, Pacific and Southern Oceans.

If the earth’s lowest spots aren’t in the middle of the ocean, where are they?

The lowest spots appear to occur along the edges of the continental boundaries.

Focus on the west coast of South America, and in the space below complete the topographic profile of the Pacific Ocean floor from South America westward about 600 miles (1000 km). Take a digital photograph of your sketch to include in your lab report.

Using Google Earth, “fly to” Challenger Deep, the deepest place on Earth (once Google Earth gets you there, you may have to zoom out to see where you are). Where is it?

The Challenger Deep is located in the Pacific Ocean, East of the Philippine Islands.

Challenger Deep reaches 11 km (11,000 meters, equivalent to 36,000 ft) below sea level. Which is greater, the elevation of Mt Everest above sea level (see Question 3), or the depth of Challenger Deep below sea level, and by how much?

The depth of the Challenger Deep is greater by approximately 2000 meters.

In the space below, give the locations of three other ocean trenches on Earth.

Tonga Trench – Second deepest trench located East of the Australian continent and North of New Zealand.

Kuril-Kamchatka Trench – Located on the Eastern edge of Russia.

Kermadec Trench – Located South of the Tonga Trench and North of New Zealand.

SEISMIC PATTERNS

Describe any patterns you see in the distribution of earthquake epicenters over the Earth’s surface – do they form lines, arcs, circles or clusters? Are patterns connected or disconnected?

The epicenters are mostly distributed around coastal lines. They are distributed unevenly with most found along the edges of plates. They form lines and clusters around the edge of the land and the patterns appear connected.

Look closely at and around the Earth’s ridges and trenches. The earthquake depth patterns associated with these features are different. Complete the chart below:

 In the vicinity of ridges.(Scan 1500km or so on either side)In the vicinity of trenches.(Scan ~1500 or so km on either side)
Describe the depth or range of depths of earthquakes, and the distribution (symmetric or asymmetric?)Is there any pattern to the depth distribution?Depths occur in a narrow range, around 150 to 200+kmThese earthquakes seem fairly evenly distributed and at similar depthsDepths occur at a wide range from as little as 8km and exceeding 200km These earthquakes appear more random, in very close proximity to each other and their depths have little consistency

Using earthquake depths as evidence, is the Earth’s lithosphere thicker in the vicinity of ridges or in the vicinity of trenches? Justify your answer.

The Earth’s lithosphere is thicker in the vicinity of trenches.

VOLCANO PATTERNS

Leaving the earthquake layer on, click on the Active Volcanoes layer. Describe the relationship between the locations of most active volcanoes and locations of earthquakes:

There is a relationship between the locations of the most active volcanoes and the locations of earthquakes. The two very nearly mirror each other.

PLATE BOUNDARIES

Where is this plate boundary, relative to the coastlines of Africa and South America?

It is in the middle of the Atlantic Ocean.

Now click the other layers on and off so that you can see relationships between plate boundaries and these features. If you did not have the “plate boundary layer” available to you, how could you determine where this plate boundary was? Be sure to consider topography/bathymetry as well as the earthquake and volcano layers. List several ways and be specific.

Without the plate boundary lines, it would be rather easy to determine where the boundaries are. Features that look like long lines, or wrinkles, appear along many boundaries that fall in an area of the ocean.

Where is this plate boundary, relative to South America?

South America’s western plate boundary meets with the Nazca Plate along the West Coast of the country.

If you did not have the “plate boundary layer” available to you, how could you determine where this plate boundary was? List several ways and be specific.

You could use the long trench that appears near the Western edge of the country. The trench indicates where the two plates meet.

PLATE MOTION

How many million years (abbreviated Ma) does each colored band represent?

Each band represents 10 million years.

On average, continental crust is 2 billion years old; the oldest rocks are 3.8 billion years old, and some of the grains in those rocks are even older.

What is the age of the oldest seafloor?

170 to 180 million years old.

On average, which is oldest – the continents or the ocean basins?

The continents.

Find the South American plate, the African plate, and the Mid-Atlantic Ridge that marks the boundary between them. What happens to the age of the seafloor as distance increases away from the Mid-Atlantic Ridge?

The seafloor age increases.

Is the crust being created or destroyed at this plate boundary (and other spreading ridges)?

The crust is being created.

Is this plate boundary divergent, convergent, or transform?

It is divergent.

Focus on the northern Atlantic Ocean, near the east coast of the US and the northwest coast of Africa. How long ago did the northern Atlantic Ocean begin to open up or start spreading? Describe your reasoning.

About 150 – 160 million years ago. As you move away from the plate boundary, the seafloor age increases as indicated by the color change. As you get closer to the continent the color turns to a deep blue/purple color, which corresponds with the 150 – 160 Ma range.

Did the northern Atlantic Ocean basin start to open at the same time as the southern Atlantic Ocean basin? How much older or younger is the northern Atlantic basin than the southern Atlantic basin? Describe your reasoning.

The Northern and Southern basin did not begin to open at the same time. When you compare the seafloor age patterns, it can be seen that the Northern basin is much older. The oldest seafloor age in the southern basin is around 120 – 130 million years old while the age in the Northern basin is 170 – 180 million years old; a difference of about 40 million years.