Study gudieeee

• Types of Volcanic Eruptions, how are they different from one another

Composite Volcanoes

a volcano composed of alternating layers of ash and lava flows with a broad base, steep sides, and often a crater at the top; also called a stratovolcano. Mt Fuji is an example. 

Shield Volcanoes

a type of volcano built almost entirely of fluid lava flows, characterized by its large width and relatively low height. Mauna Kea on the Big Island of Hawaii is a classic shield volcano.

Cinder Cones

a smaller volcano composed of small rock fragments that grows rapidly but only erupts over a short period of the time. A lava fountain erupts from Pu'u O'o, a cinder cone on Kilauea. 

• Do all volcanoes pose the same risk? All volcanoes do not pose the same risk. They do not pose the same risk since it depends on the type of eruption history, proximity to populated areas, activity level, and the nature of its eruptions. 

• Volcanic Eruptions Key Factors

• Magma viscosity (thicker magma = more explosive)

• Gas content (more trapped gas = bigger explosion)

• Plate tectonics (subduction zones = violent eruptions)

• Lava temperature and composition

• 2 types of crust 

Oceanic Crust – Denser, thinner, mostly basalt. 70% of earths surface. 3-10 km thick. Younger than continental. Made at mid Atlantic ridge. Low viscosity. 3.0 g/m density. oceanic crust is mafic.

2. Continental Crust – Less dense, thicker, mostly granite. 29% of earths surface. Older than oceanic crust. 4 billion years old. Congenital crust is pelsic. Has a high viscosity, and a 2.7 g/m density.

• Basalt vs granite (density, found) Which is more dense?

Density: Basalt is denser than granite.

• Found: Basalt in oceanic crust; granite in continental crust.

• Characteristics of EQ waves (P and S waves)

Characteristics of Earthquake (EQ) Waves

• P-waves (Primary) – Fastest, travel through solids & liquids, compressional.

• S-waves (Secondary) – Slower, travel only through solids, shear motion.

• EQ Gizmo’s- reading the seismogram and graph/time travel

Identify P- and S-wave arrival times.

• Use the time difference to determine distance from the epicenter.

• How to find an epicenter

Measure P- and S-wave time difference from at least 3 seismographs.

2. Use a time-travel graph to find distance.

3. Draw circles around each station with the corresponding radius.

4. The intersection of circles = epicenter.