{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

03_igneous_rocks_09_post

03_igneous_rocks_09_post - Lecture 3 Igneous rocks Why is...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 5: 1 Lecture 3: Igneous rocks Kilauea Volcano, Hawaii. Photo: USGS Lecture 5: 2 Why is this topic important? Igneous rocks reveal hints about the composition and pressure- temperature conditions of rocks that were melted to form igneous rock. Lecture 5: 3 Why is this topic important? Igneous rocks are associated with volcanism, which forms a significant geologic hazard 1991 Eruption of Mt. Unzen, Japan Photo: AP Lecture 5: 4 Basics: Intrusion & extrusion Magma : molten rock derived from melting of the mantle or crust Magma -- generally less dense than surrounding rocks Rises to surface Fig. 6.2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Lecture 5: 5 Basics: Intrusion and extrusion Lava : magma that has reached Earth’s surface Pluton (igneous intrusion) : magma that has intruded other rocks Fig. 6.2 Lecture 5: 6 Plutons Fig. 6.12 At time 1: Magma (red) intrudes older intrusions (gray) and sedimentary layers (brown); some magma reaches Earth’s surface to form volcanoes and lava flows At time 2: Following cooling and erosion Lecture 5: 7 Basics: Types of plutons Dike : tabular pluton that cuts across layering in intruded rock Fig. 6.10 Lecture 5: 8 Basics: Types of plutons Sill : tabular pluton that is parallel to layering in intruded rock Fig. 6.10
Background image of page 2
Lecture 5: 9 Plutons Fig. 6.12 Batholith Batholith : the largest pluton Lecture 5: 10 Basics: Types of plutons Batholith : the largest of plutons Sierra Nevada batholith, Yosemite National Park, California. Photo: R.W. Schlische Batholith Batholith Lecture 5: 11 Basics: Texture Thin sections Phaneritic : coarse-grained Aphinitic : fine-grained Photos: R. Siever Texture : size and arrangement of mineral grains in a rock Lecture 5: 12 Basics: Texture Porphyritic : large crystals in fine-grained matrix : large crystals in fine-grained matrix Photomicrograph (50x) of porphyritic andesite with phenocrysts of hornblende (brown) and plagioclase (white). Photo: P. L. Kresan
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Lecture 5: 13 Basics: Texture Pumice Ash Obsidian Glassy : no crystalline grains Pyroclastic : composed of lava fragments Photos: C. Clark Lecture 5: 14 Basics: Composition “Dark”-colored “Dark”-colored “Light”-colored “Light”-colored Mafic : “dark”-colored igneous rocks, rich in minerals containing magnesium and iron (Fe). Felsic : “light”- colored igneous rocks, rich in quartz and feldspar minerals Photo: C. Clark See Fig. 6.17 Lecture 5: 15 Review Questions 3-1. A. True / B. False: Magma is the term for molten rock below the Earth's surface. 3-2. A. True / B. False: A dike is a tabular igneous intrusion that is parallel to layering. 3-3. The largest pluton is a ___. A. Batholith B. Dike C. Sill
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}