Metamorphic rocks Vocabulary to know: Metamorphism-regional, contact, hydrothermal Recrystallization Foliated Non-foliated Porphyroblast Rock Cycle Metamorphic rocks

Heat and Pressure Change Rocks Metamorphism- the process in which an existing rock is changed by heat, pressure or both

Metamorphic rock The original sedimentary rock or igneous rock is called the PARENT ROCK Limestone is the parent rock of MARBLE (a metamorphic rock)

Metamorphic rock Rocks DO NOT melt when they undergo metamorphism

Metamorphic rock Recrystallization- when heat and pressure break the bonds that join atoms in minerals and these atoms join together differently (new bonds) Crystals can grow larger Atoms can combine in different ways

Metamorphic rock Changes can occur over large and small areas

Changes Over Large Areas Temperature AND pressure is HIGH Regions where large blocks of rocks are pressing together and pushing up mountain ranges. Can affect an area hundreds of km wide and tens of km deep

Changes Over Small Areas Mainly due to HIGH TEMPERATURE not pressure Magma can push into rocks underground, or surface rock can be covered by lava flow Rocks get BAKED not squeezed Rocks can also be changed by earthquakes (pressure can cause rocks to grind together)

Types of Metamorphism Different combinations of temperature and pressure result in different types of metamorphism Regional metamorphism Contact metamorphism Hydrothermal Metamorphism

Regional Metamorphism When temperature and pressure effect LARGE regions of Earth’s crust Can be low, intermediate or high grade The grade reflects the relative temperature and pressure (low grade being low temps and pressures)

Contact Metamorphism when molten rocks come in contact with solid rock. High temperature and moderate to low pressure Results in large scale mineral changes with little deformation

Hydrothermal Metamorphism When very hot water reacts with rock and alters its chemistry and mineralogy Fluids can dissolve, break down or deposit minerals Common around active volcanoes

Metamorphic rock Most metamorphic rock develop bands of minerals

FOLIATION An arrangement of minerals in flat or parallel bands

Foliated rocks Develops when minerals flatten or line up in bands or wavy layers.

Foliated rocks Low levels of metamorphism make extremely THIN bands Higher temperatures and pressure cause the mineral mica to grow and makes the rock look SHINY Even higher levels of metamorphism causes the minerals in the rock to separate into light and dark bands

Foliated rocks SLATE

Foliated rocks PHYLLITE

Foliated rocks SCHIST

Foliated rocks GNEISS

Nonfoliated rocks Does NOT split into layers This can happen in two ways: Rock made of mainly ONE type or mineral such as marble Has NOT been subjected to high PRESSURE such as hornfels

Nonfoliated rocks Quartzite

Nonfoliated rocks Marble

Porphyroblasts Large crystals that form in solid rock by the reorganization of atoms during metamorphism Found in areas of both contact and regional metamorphism

The Rock Cycle Rocks change but the change usually occurs over a huge span of time-thousands to millions of years

The Rock Cycle The continuous changing and remaking of rocks

The Rock Cycle

The Rock Cycle Lets try to explain the rock cycle as a class!

The Rock Cycle

ROCK TYPES Rocks are classified by how they are formed. The three types of rocks we earned about in this unit: igneous, sedimentary and metamorphic rocks.