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 mineralsNotice 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 102answer in notebook

Self check – 2,3,4 Applying skills