VOLCANOES AND EARTHQUAKES

WATCH THE FOLLOWING VIDEOS ABOUT EARTHQUAKES AND VOLCANOES.

https://www.youtube.com/watch?v=_r_nFT2m-Vg

EARTHQUAKES

https://www.youtube.com/watch?v=VNGUdObDoLk

VOLCANOES

CASE STUDIES

MOUNT ST. HELENSWashington State

Mount St. Helens is an active stratovolcano located in the state of Washington, United States. It is 96 miles (154km) south of Seattle, WA and 50 miles (80km) northeast of Portland, OR.

Mt. St. Helens’ volcano is above an active subduction zone. The Juan de Fuca plate is being pushed underneath the North American plate, melting and forming a magma chamber.

The last eruption of Mount St. Helens was May 18th 1890

The magma rose inside the mountain over a period of weeks creating a bulge on the north side of the slope. On may 18th 1980, at 8.32 am a 5.1 magnitude earthquake broke the bulge loose, causing the north side to dissolve into a massive avalanche or pyroclastic flow.

This built up released pressure from gases and exploded outwards for about 15 to 19 miles away from the mountain.

Of the top of the mountain steam and ash rose 12 miles upwards, driven by a chain of explosions from the mountains core.

The eruption continued for 9 hours.

IMMEDIATE IMPACTS

57 people died (most of them were outside the evacuated zones)

400 meters of rock was blown off the top of the mountain.

Every plant and animal within 25 km of the volcano died almost 7000 species were killed.

The water produced from melting ice and snow on top of the volcano created mudflows, which choked rivers and killed all fish and water life.

Eruption also destroyed 250 homes, 47 bridges, 15 miles of railways and 185 miles of highway.

Ash clogged machinery and caused traffic chaos. Airports were closed.

Telephone lines and electricity supplies were knocked out.

LONG TERM IMPACTS

Ash blocked rivers destroying popular fishing sites and causing flooding. This in turn destroyed crops and livestock.

Flooding destroyed communications such as road and railway bridges.

There was a huge cost of rebuilding infrastructure damage.

Major damage to the tourist industry as the location was closed for a long time.

POSITIVE IMPACTS (LONG RUN)

On the bright side, soil fertility improved due to the ash deposits, and the volcano is now carefully monitored.

Tourism has increased on the long run, boosting local economy.

SAN ANDREAS FAULTCalifornia state - Mexico

SAN ANDREAS FAULT

San Andreas Fault is a continental transform fault that extends roughly 1200 km, From California all the way down to Mexico.

It forms a tectonic boundary between the Pacific Plate and the North American Plate.

It is one of the few places in the world where you can actually stand with one foot on one tectonic plate, and the other foot on another.

It is called a strike slip fall, a place where to plates collide, and move past each other. As these plates move or creek in different directions sometimes they get stuck, the longer they get stuck, the more tension builds and the bigger the eventual earthquake.

SOME FACTS

The fault belongs to the Pacific Ring of Fire, an arc around the Pacific Ocean where many volcanoes and earthquakes are formed.

The San Andreas Fault and its branches triggers more than 10.000 quakes each year

Some of the most notable ones are: San Francisco, California April 18th, 1906 (Magnitude7.9); Parkfield, California September 28th, 2004 (Magnitude 6.0); Baja California, Mexico April 4th, 2010 (Magnitude 7.2); Ridgecrest, California July 5th, 2019 (magnitude 7.1);

BAJA CALIFORNIA EARTHQUAKE

April 4th, 2010

Magnitude 7.2 (Richter scale) - Mercalli intensity IX (Violent)

Total damage 1.5 billion dollars

2-4 dead, 100-233 injured

Occurred in the twin cities of Mexicali and Calexico on the Mex-US border.

RIDGECREST EARTHQUAKE

July 5th, 2019 8:19pm

Magnitude 7.1 (Richter scale) - Mercalli intensity IX (Violent)

Total damage 1 billion dollars

1 dead, 25 injured

Occurred north and Northeast of the town of Ridgecrest, 200 km from Los Angeles.

It was the strongest earthquake of the millenium in California

THE BIG ONE

Even though earthquakes cannot be predicted, scientist believe that a big earthquake will hit the south part of California.

Studies of the San Andreas Fault show that it has reached sufficient stress lever for an earthquake of magnitude greater than 7.0

It would be strongly felt throughout southern california and Northwest Mexico.

ACTIVITY

ANSWER THE FOLLOWING QUESTIONS…1. What type of volcano was Mt St

Helens? What are the other types, and what are their characteristics?

2. Explain how a volcanic eruption happens in your own words.

3. What is the ring of fire?

4. What is the VEI scale?

5. What are some of the positive effects of a volcanic eruption?

6. In your own words explain how earthquakes happen.

7. What do earthquakes and volcanoes have in common?

8. Where do most earthquakes take place? why?

9. What are the positive effects of earthquakes?

10.How is the magnitude of earthquakes measured.