"Rock Hound's" Webquest
Mystery Rock 1

What kind of a rock is this?

Where Found?  |  Rock formations?  |  Layers?  |  Smushed Together?  |  Geology Tests? | More Information

 

 

Where did I find this rock?

In the Chena State Park, I was hiking where there were lots of dormant volcanoes.

  

  

Chena Hot Springs  
(Chena State Park
Angel Rocks Trail 
(Chena State Park
Granite Tors Trail
(Chena State Park)

 

 

 

 

What rock formations are in the area where I found this rock?

In the Chena State Park, there is lots of evidence that volcanoes were once active here.  The Chena Hot Springs and the Granite Tors along the Angel Rocks Trail are two examples of volcanic evidence.

Chena Hot Springs



Chena Hot Springs  
(Chena State Park)


Under the Brooks and the White Mountain ridges, the top layer of earth is very thin.  In some areas, cracks or vents allow water from lakes, rivers, and melting snow to reach the super heated rock and magma below the Earth's surface.  This super heated water then rises to the surface in the form of springs.  In the Chena Hot Springs, when the water reaches the surface, it is near 150 degrees Fahrenheit.  It is cooled by the air until it reaches about 104 degrees Fahrenheit and then it is moved into the rock pool. Ahhh, soaking in this hot mineral water felt so great after a long hike!

 

Granite Tors


Granite Tors along the 
Angel Rocks Trail 
(Chena State Park)


About 80 to 60 Million years ago, hot magma flowed towards the surface but slowly cooled before actually reaching the surface.  This created huge pieces of igneous rock.  Over the years, weathering and erosion have eroded away the surrounding earth and exposed these strange looking rock features. Awesome!!!

 

 

Did my rock sample come in layers?

Sedimentary rocks often form in layers as seen in much of my hiking in the Gates of the Artic National Park.  The rocks that I am trying to identify are not formed in layers.

  

My Rock Does Not Have Any 
Layers Like the Rock in the Picture Above.

 

 

 

 

Does my rock sample look like a bunch of rocks that have been    smushed together?

Conglomerate rocks form by rocks pressing together to form a new type of rock as seen in much of my hiking in the Denali National Park.  The rocks that I am trying to identify are not formed by having many pieces smushed together.

  

My Rock is Not Smushed Together Like the One in this Picture

 

 

 

 

How would a geologist test this rock?

Tests What to do What I found out about 
Mystery Rock #1
General Description What is the grain size and texture of your rock?  Are there flecks of shiny material?
The grain size is course,  the texture is granular, and there are a few flecks of shiny material.
Color Look at the sample and determine its color - white, black, green, clear, etc
There are flecks of dark gray, light gray, and white; giving it an overall appearance of gray.
Luster
Look at the sample to determine if the mineral is metallic in appearance (looks like a chunk of metal) or non-metallic (doesn't look like a chunk of metal).

There are a few flecks of shiny material.
Hardness
Scratch the unknown rock with a known hardness to determine which is harder. Continue doing this with harder or softer minerals from the kit until the hardness is determined.
 
The sample is not scratched by an iron nail (4.5) but is scratched by glass (6) so I would say it's hardness is around 5.5 on the MOHS hardness scale.
Streak
Rub your rock across  a piece of  tile (unglazed side) and determine the color of the powder. 

The sample makes a light gray streak.

Fracture


Examine the mineral for areas where the mineral is broken. Is the break irregular or smooth?

Where the rock was broken, it has many indentations and parts sticking out.  The fracture was irregular.

 

 

 

First, I took my guide and looked through it and found two or three rocks that looked like mine.  Then, I compared the data I collected on this rock to information that I found in National Audubon Society Field Guide to North American Rocks and Minerals.  If I identified the rock sample correctly, I made an identification card.  If I felt that was not the correct identification, I went back and reviewed my data and made another educated guess.

 


Granite
g

Color  Luster  Hardness Streak  Fracture
Gray Small Flecks of Shiny Material 5.5 Light Gray Irregular

Submitting "Rock Hound":  Matthew Durant  Boston, MA

 

 

 

I want to learn more about igneous rocks

How Igneous Rock is Formed  Good description of how igneous rocks are formed.  The site offers several examples of igneous rocks.

Igneous Rocks  Excellent descriptions on how igneous rocks are formed.

Intrusive Igneous Rocks  Great images and descriptions of igneous rocks that are formed intrusively.

Igneous Rocks  Great images of igneous rocks.

Kinds of Volcanoes   Great images of the different types of volcanoes.

Volcanoes  A great description of how a volcano works.

Ask-A-Geologist  Ask-A-Geologist questions are answered by USGS employees, retirees, and contractors who have volunteered to participate in the project.

 



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