These videos explain concepts from each lecture that student often have questions about.
       

Minerals

      
Mineral cleavage - If a mineral breaks to form distinct planar surfaces that have a specific orientation in relation to the crystal structure, then we say that the mineral has cleavage.

 

  
Mineral striations - striations are the convergence or juxtaposition of two crystal faces. One of the faces gets truncated or "overtaken" by the other, but manages to leave its mark in the form of an almost imperceptible edge or stria. This edge is repeated again and again as the mineral grows and can fill an entire face with these tiny edges or striations.    
Mineral hardness and bond strength - hardness is a measure of the relative ability of a mineral to resist scratching, and therefore represents the resistance of bonds in the crystal structure to being broken.    

Igneous Rocks

      
 

Igneous Rock Classification Chart - This chart illustrates the cooling history and chemical changes associated with common igneous rocks.

The TEXTURE terms on the left, in blue and green, are associated with whether the rock cooled slowly, deep within the earth (phaneritic) or rapidly near or at the surface (aphanitic).

The CHEMICAL terms in gray across the top reflect the changing amounts of (Iron-Fe...Magnesium-Mg) and Silica.
Silicic rock are light colored.
Mafic rocks are black.

 

    
Bowen's reaction Series

The important concept to remember about this chart is:

  - dark minerals tend to solidify first. Close to 1200O C.

  - light colored minerals tend to solidify last.  Close to 800O C.

  - quartz is the last mineral to become solid.

  - as solid rocks melt, the order is reversed.  Quartz melts first and dark minerals melt last.

 

 

  

Volcanoes

      

Why are some explosive while other are not?

Explosive volcanoes has a magma composition which is high in silica while non-explosive volcanoes are low in silica.  High silica magma is thick and allows for more gases to be trapped within them.  When the pressure confining the magma is released the gases evolve explosively.

 

 

 

  

Weathering

      
 

Mechanical (Physical) Weathering - a set of 5 processes which break rocks into smaller pieces. 

1. frost wedging
2. salt wedging
3. biological wedging
4. unloading
5. thermal expansion

 

 

 

  
 

Chemical Weathering - a set of 3 processes which change the mineral composition of a rock or dissolve the rock.

Hydrolysis literally means reaction with water.  All of these processes involve water.

1. ion exchange
2. dissolution
3. oxidation
 

 

 

  

Sedimentary Rocks

      

Depositional Environments explained

Near Source (Breccia, Conglomerate)
Downstream (Arkose sandstones, Quartz Sandstone)
Swamp (Coal)
Beach (Quartz sandstone, Coquina)
Playa lakes/basin (evaporates: gypsum, chert)
Offshore (Siltstone, Shale, Limestone)