Looking at the pictures, what do you think metamorphic rocks are? Bell ringer: Looking at the pictures, what do you think metamorphic rocks are?

What are Metamorphic Rocks? Metamorphism means “to change form”. Metamorphic rocks are rocks that form when existing rocks are changed by heat and pressure. The existing rocks that are changed can be any of the 3 rock types: igneous, sedimentary, & even other metamorphic rocks.

What determines which metamorphic rock will form? 1. Starting minerals in the parent rock (protolith) 2. The agent(s) of metamorphism acting upon the rock.

3 Agents of Metamorphism Heat Pressure 3. Fluids (Hydrothermal Solutions)

Heat Two main sources: 1. Heat from magma, (“bakes” the rock) 2. Heat from increasing temperature due to increasing depth. Heat can cause recrystallization and chemical reactions, which can cause new minerals to form.

Pressure Causes Burial of rock Pressure due to tectonic plates. Effects Usually heat and pressure work together, because both increase as you go deeper in the Earth. At high temperatures and pressures, most rocks break down and change into a different arrangement of minerals that are stable in the new conditions. Mineral grains get squeezed together with pressure and become more compact (thus more dense). Pressure can orient minerals into layers (foliation).

Write your questions: Level 1 Level 2 Define Compare Describe Contrast Identify Group List Sequence Name Explain Classify/Categorize Give the relationship Cause/Effect 2 “Level 1” Questions & 2 “Level 2” Questions

Foliation vs. Stratification Don’t get foliation confused with stratification. Stratification is a characteristic of sedimentary rocks, whereas foliation is a characteristic of metamorphic rock. ?

Stratification (SEDIMENTARY rocks) When sediments are deposited, they are laid down in layers.

Sketch in your notebook Stratification Sketch in your notebook (Sedimentary Rock)

Foliation (METAMORPHIC rocks) Some metamorphic rocks become foliated when exposed to heat and pressure. This happens when pressure forces the mineral grains to grow and line up in parallel layers. The rock’s minerals become layered in sheets or the rock can appear banded.

Sketch in your notebook Foliation (Metamorphic Rock) Sketch in your notebook

Fluids (Hydrothermal Solutions) Many chemical reactions require water. Water contains dissolved minerals and/or dissolved ions, which can be exchanged between the solution and the rock. This changes a rock's chemistry (chemical makeup) rather than just the way the minerals are arranged.

Types of Metamorphism Regional Metamorphism Contact Metamorphism

Write your questions: Level 1 Level 2 Define Compare Describe Contrast Identify Group List Sequence Name Explain Classify/Categorize Give the relationship Cause/Effect 2 “Level 1” Questions & 2 “Level 2” Questions

Regional Metamorphism Occurs over a wide area or region. mainly along convergent plate boundaries where mountains are built or where volcanoes form. During the process of mountain building, there is a lot of heat and pressure. It is this combination of heat and pressure that creates metamorphic rocks.

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Contact Metamorphism Occurs in specific locations through contact with magma. Occurs near igneous intrusions, where hot magma forces itself into sedimentary strata. The rocks next to the invading magma are baked.

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Classification of Metamorphic Rocks Foliated Metamorphic Rocks Nonfoliated Metamorphic Rocks

Foliated Metamorphic Rocks Foliated: Layered or banded texture due to minerals aligning in the same direction due to pressure. Sketch in your notebook Banded Texture of Gneiss Layered Texture of Schist

Nonfoliated Metamorphic Rocks Nonfoliated: no banded texture. Most contain only one mineral. For example Limestone (Protolith or parent rock) metamorphoses into Marble. Both are made of Calcite. Limestone’s calcite crystals combine to form larger interlocking crystals thus forming marble

Write your questions: Level 1 Level 2 Define Compare Describe Contrast Identify Group List Sequence Name Explain Classify/Categorize Give the relationship Cause/Effect 2 “Level 1” Questions & 2 “Level 2” Questions

Guided Summary FIRST Identify the 2 factors that will determine what exact metamorphic rock will form. (example: why will marble form in some situations and gneiss form in others?) SECOND Have your teacher check your answer before moving on to the next task. THIRD Summarize what all determines what specific metamorphic rock will form.

Example of notes follow in the next few slides