bio/geology

what are the 3 main types of rocks?

1. igneous

2. sedimentary

3. metamorphic

what is the igneous rock?

Sourced from volcanic eruptions (often times are dark in color, with some visible crystals) 

what is metamorphic rock?

 rocks that have gone through altercation (changed through applied heat and pressure) 

• Rock samples will other have alternating dark/light banding patterns or large crystals 

what is sedimentary rock?

 rocks formed from pre-existing rocks or pieces of living organisms (often sourced from area with water) 

• These rocks generally will contain fossils and will be the focus of this course/lab 

sedimentary rocks consists of these two types:

• siliciclastic

• carbonates

think fossils**

what is siliciclastic rock composed of?

• categorized under sedimentary rock

Composed of grains from eroded pre-existing rocks (broken pieces, transported, deposited & form a new rock)→ rocks that contain mineral silica

is based on particle size:

• Conglomerate/Breccia: coarse clasts (>2mm) within a fine-grained matrix

• Sandstone: Sand sized (2mm to 1/16mm) particles

  • Mostly quartz and feldspar

• Siltstone: <1/16mm particles, still visible to the eye

• Shale: Individual particles not visible to the eye, usually distinct parallel bedding

siliciclastic rocks depends on what?

the energy of the depositional environment

the beach is what kind of depositional environment of energy?

high energy environment. Think waves moving sand back & forth 

the beach is what kind of depositional environment of energy?

low energy environment (slow moving currents…can only move tiny particles in the direction of flow)

what are carbonates consist of?

• categorized under sedimentary rock

Composed of precipitated dissolved ions in the water

Two main types: Limestone & Dolomite 

We will usually look at limestone in this class

• Composed of primarily Calcium Carbonate (CaCO₃)

  • Can be from fragments of once living organisms or other biological material 

• We can fine these rocks in tropical environments
  

what role does weather play in terms of rock formation?

Rocks are broken down through the process 

two forms:

Chemical – Changes chemical composition

• Air (rust) and water

Physical – mechanical breakdown of larger rocks into smaller particles (sediment)

• Rivers, glaciers, wind, plants, etc. 

What are Steno’s Laws?

1. original horizontally

2. lateral continuity

3. superposition

what is the original horizontally principle of steno’s laws

The Grand canyon has multiple layers of sedimentary rocks which are horizontal. 

what is the laterally continuous principle of steno’s laws

Allows us to coordinate the age of rock layers across a canyon 

• Strata are continuous laterally on either side of the canyon…so we can connect these layers as if the canyon was filled

what is the law of superposition principle of steno’s laws

Oldest strata on the bottom (deposited first) and Youngest Strata on the top (deposited) last

• All weathering, offset by faults occurs later and is the youngest activity to have happened

(Think of this link building a cake 1. cake, 2. frosting, 3. 2^nd cake layer , 4. slicing the cake to serve) 

what is cross stratification

Layering of strata (rock) layers at an angle

most commonly from the movement of water and wind, with water we generally see two types:

• SYMMETRICAL: formed from water moving evenly back and forth

• ASYMMETRICAL: formed by water currents moving predominantly in one direction. 

why energy relates to grain size

Energy is required to move grains (rock pieces), where larger grains require more energy

• large grains require more energy to move

Rock will commonly be move in areas that contain moving water. 

what is graded bedding

Changes in energy can distribute different grains and tell us the direction of movement

• Looking from A to B we see energy had decreased

what is energy and fossil preservation?

Energy can transport fine grains that allow for fossil preservation (including large & small organisms)!

what are trace fossils

• Fossils left behind by organisms that show us where it spent part of its life

• Usually indicates movement, what it ate, and nesting habits

what are indicating scales

in geology we want to know how big/small something was. We often take a measurement and draw a scale bar!