Rock Basics
What is the definition of a geologist?
A scientist who studies rocks.
What are the three major groups of rocks based on origin?
Igneous, sedimentary, and metamorphic.
Define sediment and explain how erosion and deposition contribute to sedimentary rock formation.
Sediment is small, solid pieces from rocks or living things. Erosion loosens rock, and deposition settles sediment, which compacts and cements to form sedimentary rock.
How can any rock be changed into metamorphic rock, and what forces contribute to this change?
Heat and pressure deep underground can change any rock. Forces inside and at the surface contribute to this change
briefly describe three uses of sedimentary rocks.
Building material (e.g., sandstone, limestone), making cement, and decorating buildings.
list three things geologists consider when classifying rocks.
A rock is a natural solid mixture of minerals or grains. Geologists consider color, how they form, texture, and mineral composition.
Differentiate between extrusive and intrusive igneous rocks and provide examples of each.
Extrusive rocks form from lava on the surface (e.g., pumice, volcanic glass, basalt), while intrusive rocks form from magma beneath the surface (e.g., granite).
what is an example of clastic rock
Shale, breccia, conglomerate, sandstone
What are foliated and nonfoliated metamorphic rocks, and provide examples of each.
Foliated rocks have grains in parallel layers (e.g., slate), nonfoliated rocks have randomly arranged grains (e.g., marble).
example of chemical rock
Rock salt
Gypsum
Limestone
Explain the concept of grain size and give examples of coarse-grained and fine-grained rocks.
Grain size refers to the size of a rock's grains. Coarse-grained rocks have large, visible grains (e.g., granite), while fine-grained rocks have grains too small to see without a microscope (e.g., basalt).
List three uses of igneous rocks
Tools (e.g., obsidian for sharp tools), building material (e.g., granite for statues), and decorative stone floors (e.g., pumice for cleaning).
what are the three major groups of sedimentary rock
Clastic (e.g., shale), chemical (e.g., limestone), and biochemical (e.g., coal).
Classify metamorphic rocks based on the two types of arrangement of grains, and give examples.
Foliated (e.g., schist, gneiss)
nonfoliated (e.g., marble, quartzite).
example of biochemical rock
coal
limestone
Describe the characteristics of rocks with no visible grain pattern
Some rocks have no grain pattern due to quick cooling.
Describe the mineral composition of igneous rocks (what is silica?) and how silica content influences rock color.
Silica is silicon and oxygen; Silica content influences color; low silica forms dark rocks (e.g., basalt), high silica forms light rocks (e.g., granite).
Explain the processes of compaction and cementation in sedimentary rock formation.
Compaction presses sediment, and cementation glues particles together. Over time, layers build up, squeezing tightly.
What are two highly useful metamorphic rocks, and what are their respective uses?
Marble (used for buildings and statues) and slate (used for flooring, roofing, walkways, and chalkboards
explain the rock cycle providing at least 6 key terms
Igneous rocks are the starting point of the rock cycle. They can be weathered and broken down into sediments through processes like erosion.
Sedimentary rocks often result from the weathering and erosion of existing rocks. They can undergo further weathering or be buried and subjected to heat and pressure, leading to the formation of metamorphic rocks.
Metamorphic rocks can be formed from the alteration of existing rocks in response to changes in temperature, pressure, or the presence of chemically active fluids. They can also be subjected to weathering, breaking down into sediments that contribute to the formation of new sedimentary rocks.
Explain HOW geologists classify rocks based on origin and provide examples of each major rock group/it's origin
Rocks are classified into igneous, sedimentary, and metamorphic. Igneous rocks form from cooling molten rock, sedimentary rocks form from particles pressed and cemented, and metamorphic rocks form from existing rocks changed by heat, pressure, or chemical reactions.
Explain the texture of extrusive and intrusive rocks and how it is related to their cooling rates.
Extrusive rocks have small, rapid-cooling crystals, while intrusive rocks have large, slow-cooling crystals.
Porphyritic rocks form in two stages with both large and small crystals.
Differentiate between clastic, chemical, and biochemical rocks based on their formation.
Clastic rocks form from rock fragments, chemical rocks from crystallized minerals, and biochemical rocks from plant and animal remains.
Describe the characteristics that change in metamorphic rocks and how they can form from different rock types.
Changes include appearance, texture, crystal structure, and mineral content. Metamorphic rocks can form from igneous, sedimentary, or other metamorphic rocks.
what is the difference between a porphyritic texture and a glassy texture
The key difference between porphyritic and glassy textures lies in the presence or absence of visible mineral grains. Porphyritic rocks have both larger crystals (phenocrysts) and a finer-grained matrix, while glassy rocks lack visible mineral grains altogether and have a smooth, glass-like appearance. The formation conditions, cooling rates, and the overall visual appearance distinguish these two textures in igneous rocks.