Class Announcements
This presentation is the property of its rightful owner.
Sponsored Links
1 / 28

Class Announcements PowerPoint PPT Presentation


  • 64 Views
  • Uploaded on
  • Presentation posted in: General

Class Announcements. Term Break extra credit option due Friday at class time. Sign up today to attend a Papago Park extra credit field trip (worth 20 points). Options: Wed., April 16: 10-11AM or 4-5 PM Thurs., April 17: 10-11AM or 2-3 PM. Today’s Lecture: Chapter 9 Volcanic activity.

Download Presentation

Class Announcements

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Class announcements

Class Announcements

Term Break extra credit option due Friday at class time.

Sign up today to attend a Papago Park extra credit field trip (worth 20 points).

Options:

Wed., April 16: 10-11AM or 4-5 PM

Thurs., April 17: 10-11AM or 2-3 PM


Class announcements

Today’s Lecture: Chapter 9

Volcanic activity

Class presentations:

Mexican Volcanoes - Shawn Brown

Dissolved gases, silica content and explosiveness of eruptions

Silicic volcanoes

Intermediate volcanoes


Class announcements

  • lava

  • gases

  • pyroclastics

Materials extruded during an eruption

2. Materials extruded during an eruption

Magmas contain dissolved gases, held in by pressure!

1-6% by weight,

Mostly water vapor

Gases (volatiles)

gases expand causing lava and volcanic rock to explode

Magma rises to surface

& pressure rapidly drops


Fig 09 08

Fig. 09.08

Stephen Marshak


Class announcements

Nature of volcanic eruptions

Importance of gas in eruptions

Expanding gas provides the force to fragment

and violently expel molten rock & ash.


Class announcements

  • lava

  • gas

  • pyroclastics

Materials extruded during an eruption

2. Materials extruded during an eruption

Expanding gases pulverize rock, forming ash.

Violent escape hurls ash, blocks of rock

and blobs of magma into the air above the

volcano

Pyroclastic materials


Class announcements

Silica-rich magmas produce

explosive eruptions.

  • Violent volcanic eruptions produce:

  • rock fragments

  • finely fragmented ash

  • molten bombs

  • large angular blocks

These accumulate

to form:

pyroclastic

volcanic

rocks


Class announcements

Three basic general volcano types:

a. Shield volcanoes

b. Cinder cones

c. Composite cones

  • Composed of

  • pyroclastics

  • Small, steep sided

  • cones

  • Sometimes have

  • associated flows


Class announcements

Cerro Negro

Nicaragua


Class announcements

San Francisco Volcanic Field, AZ


Class announcements

Sunset crater, AZ


Class announcements

Types of Volcanoes

a. Shield volcanoes

b. Cinder cones

c. Composite cones

  • Symmetrical form

  • Intermediate size

  • Alternating lava flows

  • & pyroclastic deposits


Class announcements

Mt. Fuji, Japan

Composite

volcanoes

erupt

pyroclastics

and lava in

~ equal

Proportions.

Mt. Mayon, Philippines


Class announcements

Intermediate and silicic volcanism

Most found above subduction zones.

Subduction zones


Class announcements

Andes


Class announcements

Mt. Shasta, CA


Class announcements

Mt. Fujiyama, Japan


Fig 09 05a

Fig. 09.05a

Stratospheric haze

Rising column

W. W. Norton

Collapsing column

Falling lapilli

Nuée ardente

Features of Explosive

Volcanic Eruptions


Class announcements

Hot ash clouds are denser than air

and may collapse and rush down

volcanic slopes at high speeds forming

a nuee ardente (fiery cloud) or ash-flow.

Pyroclastic flows


Fig 09 01a

Fig. 09.01a

Stephen Marshak


Fig 09 01b

Fig. 09.01b

Stephen Marshak


Class announcements

Body cast of

Pompeii victim.

A mold was

formed

when hot ash

congealed

around body,

burning it away to

leave a mold.


Class announcements

  • lava

  • gas

  • pyroclastics

Materials extruded during an eruption

2. Materials extruded during an eruption

If hot ash is erupted onto snow, or a lake,

or if once deposited, ash becomes

saturated by rain, volcanic mudflows

may form. These are highly fluid mixtures

of water, ash and rock that travel downslope

at very high speed, burying whatever is in

their path.

Volcanic mudflows or “lahars”


Fig 09 07

Fig. 09.07

U.S. Geological Survey

Mount Saint Helens Mudflow


Class announcements

Volcanic hazards

map for

Mount Rainier WA


  • Login