Basaltic Volcanism-A Quick Guide
Cochise College
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Roger Weller, geology instructor                       

wellerr@cochise.edu    copyright 2011

 

Basalt

There are 5 major types of basaltic volcanism:
     lava flows
     cinder cones
     shield volcanoes
     flood basalts
     maars


1. Lava Flows

There are two types of basaltic lava flows. 
The first type produces a smooth to ropey surface. 
This type is known as
pahoehoe
This flow occurred on the big island of Hawaii.




Here is another view of pahoehoe.
This is from Craters of the Moon National Park in Idaho.


Here is a close up view of ropey pahoehoe.




The second type of lava flow is made of sharp, angular fragments. 
The Hawaiians named this type of lava
aa
Here is some aa lava from the Craters of the Moon National Monument in Idaho.




Arizona also has some aa lava flows near Flagstaff.



2. Cinder Cones

Cinder cones are relatively small volcanoes,
often no more than one half to two miles wide. 
They are made of of loose cinders.

Here is a cinder cone at the top of Haleakala in Maui, Hawaii.




Here is another cinder cone, the youngest volcano in Arizona, Sunset Crater.




Cinder cones weather quite fast.  Here is a weathered cinder cone
in the
San Bernardino valley in the southeastern corner of Arizona.



3.  Shield Volcanoes

Shield volcanoes are large and have low profiles.
This is Lanai off the coast of Maui, Hawaii.


 

Above the clouds, Haleakala on Maui, Hawaii .

.

4. Flood Basalts

Flood basalts are enormous flows of lava from fissures that cover many square miles.
Below is a view of Craters of the Moon National Monument in Idaho.



5. Maars

Maars are large craters produced by explosive basaltic eruptions.
Cerro Colorado in northern Mexico.


 

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