UW-GEOLOGYName:
IGNEOUS ROCKS AND THEIR TECTONIC CONTEXT
Put your responses to the following questions directly on this page.
Partial melting of a rock:
Open the following link, follow the animations and then answer the questions below:
1.a.What three things govern whether a rock will melt?
b.What is the “dry melting curve?”
c.How does melting occur at the mid-ocean ridge?
d.How does water affect melting?
e.Where, tectonically speaking, does water play a role in magma production?
f.Explain how partial melting can produce a magma of different composition than the starting rock.
Bowen’s Reaction Series:
Open the following link, follow the animations and then answer the questions below:
2.a.How is Bowen’s reaction series different from partial melting?
b.Why does basaltic lava flow so easily?
c.What minerals make up basalt?
d.Where do andesitic magmas form (tectonically)?
e.What minerals are common in Rhyolitic magma?
f.How can the same volcano produce both volcanic tuff and obsidian?
g.What is the difference between the continuous and discontinuous series?
Igneous rocks around the tectonic world:
Use the following plate tectonic map to answer questions 3 and 4
3. Find the East Pacific Rise on the Plate Tectonic Map.
a. What type of plate boundary is this?
b. What type of igneous rock is produced here?
c. What kind of ocean floor topography would be produced here?
- Explain why and how this particular type of igneous rock is formed at this type of boundary.
4. Find the west coast of South America on the Plate Tectonic Map.
a. What type of plate boundary is this?
b. What type of rock is produced here? (give both the intrusive and extrusive varieties)
c. What topographic feature is produced at this kind of plate boundary?
d. Briefly explain why and how this particular type of igneous rock is formed at this type of boundary.
5.Look at the following picture.
The picture shows the famous Half-Dome in the Sierra Nevada batholith, a 500-mile swath of granite in central California.
a. Briefly explain how and where a magma with a composition of granite could form.
b. Geologically speaking, what must have happened (after the granite had cooled) to allow these huge cliffs to be climbed?
6.Hawaii. Look at your Plate Tectonic map and find Hawaii. The Hawaiian Islands are seamounts, part of the Hawaii-Emperor chain.
a. What kind of igneous rock would you expect to be forming the Hawaiian/Emperor seamounts?
b.How is the magma formed that produces this kind of igneous rock?
c. Mauna Kea on the island of Hawaii rises 4170 meters above sea level and its base is on the ocean floor at a depth of 5050 meters. Knowing that 1 meter = 3.28 feet, how tall is “Mt.” Mauna Kea?
Show your work.
d. How does this compare with Mt. Everest?
Open the following link to answer e-h.
e.What is a mantle plume?
f.Why does the mantle plume melt beneath the lithosphere?
g.Why does a hotspot volcano eventually become extinct?
h.What are seamounts?