Metamorphic Rocks Section 4-3

Metamorphic Rocks  Rocks that have changed due to heat and pressure  Banding effect – causes the minerals to become squashed in lined or banded (foliated) forming a gneiss.

2 ways gneiss is formed  Flattening due to pressure from above  Stretching due to pulling along fault lines Flattened rock with foliation versus stretched rock with lineation. Illustration by Anne Crowder. Foliation

Notice banding of minerals Notice bending of bands due to folding pressure 

Causes of heat and pressure  Heat – 1. Radioactive decay 2. Contact with magma pools  Pressure 1. Overlying rock 2. Plate boundaries

Formation of Metamorphic rocks

Classification of Metamorphic Rocks Foliated Rocks – minerals are flattened and line up in parallel bands Ex. Gneiss – forms from granite

Slate – forms from shale - minerals so tightly packed water cannot pass through

Careful on this pronunciation. There’s an “s” before the “t”.  Schist – layering of minerals  Ex. Mica schist

Metamorphic rocks that are not banded. (nonfoliated)  Nonfoliated rocks – no banding occurs  - mineral grains change, grow and rearrange  Ex sandstone (mostly quartz) – forms quartzite.

 Marble – formed from limestone

Marble  Calcite – give it a shiny appearance  Hornblende and serpentine – give it its greenish tint  Hematite – give it is reddish tint  Used in statues

Textbook page 102 answer in notebook  Self check – 2,3,4  Applying skills