Pacific Ring of Fire and Natural Disasters

Pacific Ring of Fire The “Ring of Fire” is a series of tectonic plate boundaries around

the pacific ocean.

75% of the worlds volcanoes (450 +) and 90% of the worlds earthquakes occur here.

Mariana’s Trench = deepest place on earth (Challenger Deep is 36,000 ft, 7000 ft. taller than Mt. Everest)

What is an earthquake?

A release of energy caused by the sudden movement of tectonics plates

The energy is released as “seismic waves” Like ripples in a pond

Where?

Earthquakes occur at two different plate boundaries

Subduction Zones

Plates colliding into each other

Transform Faults

Plates sliding past each other

Measuring Earthquakes…July 1976, China – 243,000 (7.8)

Dec. 2004, Indian Ocean – 230,000 (9.1-9.6)

1960, Chile – 20,000 homeless (9.5)

1964, Alaska - 132 (9.2)

2011, Japan – 16,000 (9.0)

2010, Chile – 120 (8.8)

What is a volcano?

An opening in the earth’s crust where magma (molten rock) flows from the mantle to the surface

Volcanoes and Tectonic Plates

Most volcanoes occur near tectonic “active zones”

Divergent zones – where two plates are moving away from each other (Katla volcano in Iceland)

Subduction zones – where two plates are crashing into each other (Kyushu volcano in Japan)

Classifying Volcanoes

• Shield

• Intermittent

• Dormant

• Composite or Stratovolcano

• Extinct

Constan

t

• Active

Shield VolcanoesA shield volcano is a large, gently sloped volcano made up from many slow, steady flows of hot lava. Low and broad – like a warrior’s shield.

Materials Erupted: mainly liquid lava, so the volcano is made of layers of hardened lava.

Non-explosive eruptions

Example: the volcanoes of Hawaii

Composite or Stratovolcano

A composite volcano is a huge mountain-like volcano. Layers build up like frosting on a cake forming a cone with steep sides.

Materials Erupted: sometimes lava, sometimes rock fragments.

May have very explosive eruptions

Example: Mount St. Helens

Mt. St. Helens: Before and After

Pavlov - Alaska

Mount Ontake - Japan

Sarychev - Russia

Erupting volcanoes can destroy land, plants, animals and human settlements

Volcanic eruptions include:

Earthquakes

Lava flows

Explosions of hot gas, ash and rock

Landslides and mudslides

Volcanoes also create land and life

Creating land when molten lava cools and solidifies, it turns into solid rock (this is new land)

Creating life the minerals from volcanic rock and ash create very good soil for new plants

Because of this balance of creation and destruction, people often say eruptions mark the “re-birth” of an environment