Do Now: How can or does a volcanic eruption or earthquake occur? What forces on this planet are responsible for them? Explain your answer in complete sentences. T and T

Aim: How do volcanoes and earthquakes change our planet?

Volcanoes & Earthquakes Unit 2.1b

Volcanoes Volcanoes are mountains formed when plates meet magma from asthenosphere rises through the lithosphere to erupt on the surface as lava

1. if internal pressure is high enough… Lava, ash, and gases can be ejected into the atmosphere or flow over land

Fig. 14-6b, p. 351 Extinct volcanoes Eruption cloud Ash Acid rain Ash flow Lava flow Mud flow Landslide Central vent Magma conduit Magma reservoir

2. Volcanic Activity Active volcano- has/can erupt –Magma has a direct line to the volcano and pressure exists within the volcano Dormant volcano- not known to erupt –Moving plates can connect magma to it activating it Extinct volcano- wont erupt again –Magma line cut off due to moving plates

Volcano leading to islands

3. Types of volcanoes Rift volcano- when plates move away from each other and magma creates new ocean crust Subduction volcano- when plates collide and slide over each other exposing magma Hot spot volcano- place within a plate where magma upwelling causes magma to rise to the surface –not at plate boundaries –Ex: Hawaiian Islands

F. Earthquakes (EQ) Result of vibrations deep in the earth that release energy –Usually at transform boundaries where plates grind past each other and friction builds up when they get stuck in one spot until the point where they slip past each other releasing all the energy from the friction being released Focus- where the EQ begins inside Earth Epicenter- where the EQ reaches surface

Major Features and Effects of an Earthquake Fig. 14-7, p. 351

Fig. 14-7a, p. 351 Liquefaction of recent sediments causes buildings to sink Two adjoining plates move laterally along the fault line Earth movements cause flooding in low-lying areas Landslides may occur on hilly ground Shock waves Focus Epicenter

1. Measuring EQ Seismograph- measures size (magnitude) of EQ Richter Scale- measures the amplitude of the highest S-wave of an EQ –Each # = 33x the energy compared to the previous #

Earthquakes Are Geological Rock-and-Roll Events (2) Richter scale –Insignificant: <4.0 –Minor: 4.0–4.9 –Damaging: 5.0–5.9 –Destructive: 6.0–6.9 –Major: 7.0–7.9 –Great: >8.0 Largest recorded earthquake: 9.5 in Chile in 1960

2. Major EQ features

Earthquake Risk in the United States Figure 16, Supplement 8

3. Global EQ Risk

Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis Tsunami, tidal wave –Travels several hundred miles per hour Detection of tsunamis –Buoys in open ocean December 2004: Indian Ocean tsunami –Magnitude 9.15 and 31-meter waves at shore –Role of coral reefs and mangrove forests in reducing death toll

4. EQ Effect: Tsunami Formation

Ex: Indonesia Tsunami 2004 In December 2004, a great EQ with a magnitude of 9.15 on the seafloor of the Pacific Ocean created a large tsunami that killed 168,000 people in Indonesia.

Indonesia shoreline June 23, 2004 before tsunami

December 28, 2004 aftermath from the tsunami

Shore near Gleebruk in Indonesia before and after the Tsunami on June 23, 2004 Fig. 14-9, p. 353

Summary: How do volcanoes and earthquakes impact society?