Week 8: Geology

What did you do in lab today? 

Characteristics of Sand 

1. Size 

2. Shape  

3. Color 

 

Sand Investigation  

• 1: Looks like little rocks, maybe from river 

• 2: more red-ish, maybe from the desert 

• 3: black, looks like rasins, maybe from river 

• 4: white, looks beachy, crystal like, maybe from beach 

• 5: looks crystal, colorful, maybe from cove or cave 

• 6: yellow-ish, small pebbles, from beach maybe or river 

• 7: brown, red-ish, small, from river/jungle 

• 8: Looks same as 7, small, neutral colors, maybe from river or desert 

• 9: looks like coal, black/gray, looks like from volcano (black sand beach) 

• 10: yellow, orange-ish, from desert? maybe a river, bigger pebbles  

• 11: little white rocks, looks like little eggs, maybe from desert 

What was the big question?

What is weathering and erosion?

What is the cycle of sand and rocks. 

What did you learn in Thursday's discussion?

The Devonion in Iowa  

 

• 419 to 359 million years ago  

• Warm shallow in land sea 

 

Some of the marine environment is:  

• Brachiopods 

• Trilobites 

• Corals 

• Crinoids 

• Cephalopods 

• Armored fish like Dunkleosteus (Which we saw in the Museum)\ 

 

Extensive reef systems (particularly in eastern iowa) 

 

Famous Sites – Devonian Fossil Gorge 

 

Coralville was exposed during 1993 flood and showed a direct view of an anient sea flood which is refered to as the "grand canyon of iowa" 

 

SAND 

 

Sand created through water is polished, smooth, and generally similar in size 

 
Sand created through glaciers is polished, smooth, but irregular in size (sizes all over the place) 

 
Sand created through wind is opaque, frosted, pitted (dented), and very fine grained. 

 

Extrusive: Exit earth, cool fast (water/air) small crystal 

 

Intrusive: Insidde earth, insulated by earth large crystal   

 

WEATHERING AND EROSION 

 

Weathering is the process by which rocks are attacked by the 
environment. There are two types of weathering, mechanical and 
chemical. 

 
• Mechanical weathering is simply breaking the rock down into 
smaller fragments. This process forms detrital sedimentary 
rocks. (Broken) 

 
• Chemical weathering occurs when chemical reactions alter the 
composition of a rock. The chemical sediment that forms from 
this type of erosion forms chemical sedimentary rocks. 

 
Erosion is the movement of sediment. Think: water, wind, 
glaciers. Rock is weathered (broken down) then moved (erosion). 

 

What did you learn?

Law of Superposition

In the image, above, the layers of rock oldest to youngest are C, B, A, D.

• C is the oldest because it is the deepest layer.

• Next, B was formed on top of C.

• Then, A was formed on top of B.

• D is an intrusion of magma. We can tell it happened after A, B, and C were formed because it intrudes (cuts through) through all three layers and reaches the surface of Earth.

Key Takeaway: Weathering is the making the mess and Erosion is cleaning it up.

What was most helpful? 

The videos and the visual representations of the law of superpositon 

What do you need more information on?

I am going to have to watch more videos about the fossils and different eras in geological history.