Igneous Rocks Notes
1. Igneous rocks are also known as _____________ ______________ .
2, ______________________ Igneous Rocks form when lava erupts from a volcano or “bubbles
up” from tectonic plates moving apart - onto (OUTSIDE) Earth’s surface.
Ex: Basalt – the most common extrusive rock on Earth; forms most of Earth’s ocean floor.
Ex: Obsidian – black volcanic glass
3. ________________________ forms more of Earth's surface than any other rock type. Most
areas in ocean basins are basalt and may be formed on land from lava flows, too.
4. Obsidian is a ______________ ___________________ rock formed from rapidly cooling lava
forms a fine-grained rock with no crystal structure.
Ex: Basalt - crystals too small to be seen without a microscope.
Ex: Obsidian –smooth, shiny texture like thick glass & cooled without forming crystals
“Volcanic Glass”
5. __________________Igneous Rocks forms when magma hardens beneath Earth’s surface
(INSIDE).
Ex: ____________________ – the most abundant intrusive rock on Earth’s continents. Forms
the core of many mountain ranges.
Ex: Porphyry - looks like jello w/fruit inside it
6. __________________ is used to make many objects Granite is also well-known from its many
world-famous natural exposures. These include: Stone Mountain, GA; Mount Rushmore, SD
7. Intrusive Igneous Rock are coarse-grained because slowly cooling magma forms rocks with
________________________ crystals.
8. Igneous Rocks – Mineral Composition
When magma is ______________ in silica light-colored rocks form - like granite. These are
also called _________________ igneous rocks.
When lava is _________________ in silica dark-colored rocks form - like basalt. These are
also called ____________________ igneous rocks.
Igneous Rocks Notes
9. Uses of Igneous Rock
______________________ – Statues, Bridges and old public buildings, Paving streets with
cobblestone, floors, kitchen countertops (thin polished sheets of Granite)
________________________ - Gravel for construction
___________________ - Sharp tools for cutting and scraping (Native Am!), Starting
vegetable gardens (fertilizer) – it’s called Perlite, which is formed from heating Obsidian
______________________ is cool! It can float and is used as an abrasive.
Questions…
What processes form Igneous Rocks?
How are the 2 types of Igneous Rock different?
How can we use Igneous Rocks? How have they been used in the past?
Can you describe the most common Intrusive Igneous Rock? Where is it commonly found?
Can you describe the most abundant Extrusive Igneous Rock? What area on Earth is mostly
made of this type?