Activity Sheet-3 Rocks - Lecture -- 120 points
It’s all about relationships. As you prepare for exam-1, review the content below and formulate relationships between basic mineral chemistry (composition) and textural characteristics of rocks. In many cases, don’t memorize, but explain in your own words and develop a picture in your mind regarding rocks. Most importantly, as you learn the concept and relationship, be able to explain the concept using the proper terminology. Please make sure you take a look at the probable exam essay questions at the end of this activity sheet. It’s recommended that you view the rock lecture in its entirety before answering questions.
______________________ makes minerals, _______________________ makes rocks.
Relationship questions:
Explain how a rock is different than a mineral
Write a definition of a rock ---- in your own words
Does the 5-part definition of a mineral fit the definition of rock Why or Why not?
Briefly, write your own definition of an igneous, sedimentary and metamorphic rock.
Relationship questions:
What criteria allow scientists (geologists) to divide rocks into three categories?
How does each rock group relate to the rock cycle?
Identification of rocks (igneous, sedimentary, metamorphic) is made by observing the rock's textural characteristic and its composition.
Relationship questions:
Define Texture and Composition (IMPORTANT ROCK CONCEPTS)
Draw a diagram illustrating how a geologist views the term texture when identifying a rock
Draw a diagram illustrating how a geologist views composition when identifying a rock
What geologic conditions control textural characteristics for each rock group?
Igneous Rocks
Igneous rocks are classified as either intrusive or extrusive.
Relationship questions:
Define intrusive and extrusive as it relates to igneous rocks
How do textural characteristics differ between intrusive/extrusive igneous rocks. Draw a diagram
Using the terms phaneritic and aphanitic, label your diagram and explain the geological environment producing these textures.
Compositions of igneous rocks can be identified based on the color of the rock (light, dark or intermediate colors)
Relationship questions:
What mineral compositions typically color the igneous rock dark, light and intermediate?
Describe the terms mafic and felsic with respect to mineral compositions of igneous rocks
Mafic compositions are known for high concentrations of _________________________
Felsic compositions are known for high concentrations of ________________________
6. Classification of igneous rocks is based on texture and composition. Use the igneous rock classification chart and fill the blanks below.
A phaneritic felsic igneous rock is identified as a _________________________
An aphanitic, felsic igneous rock is identified as a ________________________
A phaneritic, mafic igneous rocks is identified as a _______________________
An aphanitic, mafic igneous rock is identified as a _______________________
A phaneritic intermediate igneous rock is identified as a ______________________-
An aphanitic intermediate igneous rocks is identified as a _____________________
Relationship questions
Describe the relationship with rocks A and B , C and D and E and F. (What is similar)
Describe the differences in the geologic environment with rocks A/B, C/D and E/F (What is different?)
Sedimentary Rocks
7. Sedimentary rocks are formed from the weathering process within the “sedimentary rock cycle”. Define each term in the sedimentary cycle and arrange the terms in order that would result the formation of a sedimentary rock
LithificationWeatheringdepositionTransportation
Unconsolidated sedimentsedimentary rock
8. Sedimentary rocks are divided into 3 categories based on the type of sediment. Rather than memorize each category, provide a one to three word description of each category that clearly shows the difference
Detrital (clastic)
Chemical
Organic (bioclastic)
9. Using your answers in #8, refer to the rock lecture and identify the common sedimentary rocks that have been lithified.
Detrital: (Name the rock types according to decreasing grain size)
Chemical:
Organic:
Relationship questions:
Describe the textural differences between detrital, chemical and organic sedimentary rocks
Why is hydrochloric acid (HCL) a useful test for chemical sedimentary rocks?
Can organic and chemical sedimentary rocks react with HCL Why?
What does detrital, chemical and organic sedimentary rocks tell the field geologist about ancient geologic environments?
Metamorphic Rocks
Based on your first viewing of the rock lecture, write a brief sentence describing the general differences between igneous and metamorphic rock textures--- What do you observe?
What is a good working definition of a metamorphic rock (refer to the lecture)
Relationship questions:
What is meant by “solid-state-transformation?”
How would the metamorphic rock be classified if temperatures turned the rock into a liquid?
What depths (pressure) and temperature is considered for preexisting rocks to begin metamorphism?
Metamorphic rock geologic environments
Contrast the differences between contact and regional metamorphism on pre existing rocks. Draw a diagram that represents contact and regional metamorphism.
Relationship question;
If you understand the condition for one type of metamorphism, how would you use the conditions to learn the other type of metamorphism (contact vs. regional)
10. The geothermal gradient provides another type of heat source for metamorphism.
Observing the geothermal gradient diagram, what is the geothermal gradient telling you regarding the y-axis and x-axis?
Fill in the blanks ---- As depth increases, ____________________ increases, and ________________ increases.
Relationship questions:
If temperature was increased at a constant rate, what would the temperature gradient line look like on the geothermal gradient graph?
At what depth does the geothermal gradient rise rapidly and what depths does the geothermal gradient become less?
Why is the geothermal gradient rapid in the upper part of the earth’s interior?
11. As earth depth increases, pressure increases. Pressure on rocks is variable but can exist between two end members ---- from confining to differential type pressures.
Define confining and differential type pressures
Provide an example of confining and differential pressure
Relationship questions:
During metamorphic processes, which type of pressure do you think is dominant and why?
Describe some common metamorphic environments that would produce enough pressure to deform solid rock
How is the statement “solid-state-transformation” related to pressures deforming rock?
12. Remember that identification of rocks is a function of textural and compositional characteristics. In metamorphic rock textures, geologists use the term foliation and non-foliation for identification.
Define the textural terms “foliated” and “nonfoliated”
Provide metamorphic rock examples for foliated and nonfoliated types.
Relationship questions:
What is the pressure/temperature relationship difference between the rocks gneiss and slate?
How does grain size tell the geologist if the rock was subjected to high or low metamorphism temperatures and pressure?
If pressure and temperature conditions are great enough to exceed the solid-state-transformation state and the rock material becomes liquid, what part of the rock cycle is represented? And how does this define the “rock cycle”?
Possible essay questions
Define the differences between contact and regional metamorphism and provide two examples of metamorphic rock types
Briefly explain how the formation of each rock type (igneous, sedimentary, metamorphic) and provide three rock examples for each rock group.
How is the rock cycle related to internal and external forces?