Geology

What makes a mineral?

1. Be naturally occurring (must exist in nature) 2- Be solid 3- Be inorganic (not be made out of cells, or come from a living thing) 4- Must have a crystalline structure If you are missing even one of these criteria then the substance is not a mineral, but something called a mineraloid.

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What are properties to classify a mineral?

Color- What color is the mineral (A WEAK WAY TO TELL MINERALS APART, MINERALS CAN BE MANY DIFFERENT COLORS) Streak- What color is left behind when the mineral is scraped along a porcelain plate (a strong way to tell minerals apart- despite being different colors, a mineral will always have the same streak) Hardness- (a strong way to tell minerals apart- hardness is a mineral's resistance to being scratched. The harder the mineral the higher the number of its hardness is from 1-10. A mineral can scratch any other mineral that has a hardness lower than its own hardness) Luster- (a weak way to tell minerals apart because it is subjective)- Luster is how you describe a mineral's shininess. Shiny like metal= A metallic luster Not shiny like metal/dull= A non-metallic luster Cleavage- (a strong way to tell minerals apart) When a mineral breaks apart in a predictable way each and every time. Some minerals always break in a rhombus shape or a cube shape. There are some minerals with no cleavage and break randomly–we call this random breakage fracture Miscellaneous- (this is very situational) some minerals have specific special things about them that make them stand out easily Example- Magnetism, Smell, Reaction to Acid, Taste

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What are rocks?

Rocks are what we call a collection of different minerals. \*There are some cases where rocks are made of no minerals, but generally most rocks are made of several minerals.

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WHat are the classifications of a rock?

All of the rocks in the world can be classified into one of the following categories Igneous Rocks- A rock formed from the solidification of lava/magma Sedimentary Rocks- Rocks that formed from the broken bits and pieces of other rocks Metamorphic Rocks- Rocks that were once other rocks that have now been changed into new rocks by intense heat and/or pressure

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What is an igneous rock?

A rock formed from the solidification of lava/magma

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What are some giveaways that you are looking at an igneous rock?

You see crystals. Crystals will appear as tiny geometric shapes Crystals mean your rock grew slowly in a hot environment underground- This is called an intrusive or plutonic igneous rock No crystals means your grow grew quickly in a cool surface environment- This is called a volcanic or extrusive igneous rock The color of an igneous rock helps you classify it- Tan/whitish colored rocks are called FELSIC Igneous Rocks Black/gray colored rocks are called MAFIC Igneous Rocks (Obsidian is an exception to this rule) You see vesicles. Vesicles look like little craters or air bubbles-like you would see in a sponge’s material (picture below right)

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Intrusive

Igneous rocks that grew under the surface. ANother word of this is Plutonic.

Extrusive

Igneous rocks that grew quickly with no crystals over the surface. Another word for this is volcanic.

Felsic

Tan/whitish colored rocks

Mafic

Black/gray colored rocks

Vesticals

little craters or air bubbles-like you would see in a sponge’s material

What is a metamorphic rock?

Rocks that were once other rocks that have now been changed into new rocks by intense heat and/or pressure

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What are giveaways that you are looking at a Metamorphic rock?

Metamorphic rocks can show foliation- This means the rock looks like it has bands or stripes Metamorphic rock’s grains can look like they’ve been fused together in a pattern like a mosaic

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Foliation

the rock looks like it has bands or stripes

What is a sedimentary rock?

Rocks that formed from the broken bits and pieces of other rocks

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What are some giveaways that you are looking at a sedimentary rock?

You see small grains/clasts. Grains are usually small round (not as geometric as crystals), little rocks which are within the larger rock. It gives the idea that this rock is made of bits and pieces of many other rocks -If you see grains/clasts you are probably looking at a detrital sedimentary rock. -Do remember, some sedimentary rocks are chemically formed and have no grains/clasts. - A fossil is a give away that you are looking at a sedimentary rock. Fossils can only be found in sedimentary rocks.

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What is weathering?

Weathering is the break down of rocks that have been exposed to the atmosphere

What is Erosion?

Once the rocks are broken down, the pieces are transported from one place to another. This process is called erosion

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What can cause erosion?

This is called an agent of erosion, which is a fancy way for someone to say that something causes erosion. Erosion is caused by wind, moving water (streams, waves, ocean currents), ice (glaciers), and by gravity. Most of it is caused by moving water. Wind– This is the biggest agent of erosion in dry climates. Wind can sandblast rocks into strange shapes called ventifacts or create piles of sand dunes.

What are the agents of erosion?

Wind can sandblast rocks into strange shapes called ventifacts or create piles of sand dunes. Running water is the most commonly occuring agent of erosion that occurs in NYC, which can weather and erode the ground very quickly, and waterfalls are an example of water erosion. Gravity is also another one, and so is ice.

What is mass wasting?

Mass Movement can be caused by natural processes or human activity The major types of mass movement are-

One type is called landslides, which is when soil/rock slips off of a mountain surface. If mud falls off instead, we call it a mudslide.

Solifluction- when wet soil near the surface of the Earth moves downhill instead of into the ground because it is blocked by ice from beneath.

Creep- Creep is a slow and long term form of mass movement. The combination of small movements of soil or rock in different directions over time is directed by gravity gradually down a slop. The steeper the slope, the faster the creep.

And Slump- A slump is a type of mass wasting that results in the sliding of rock materials along a curved surface. In a slump, a portion of an entire mountain moves down a short distance.

What is ice erosion?

Ice- Glaciers are the major form of ice erosion that shape our planet’s surface. Glaciers- A large, chunk of ice, snow, rock, sediment, that slowly moves down slope under the influence of its own weight and gravity.

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What are the two types of weathering?

Physical aka Mechanical weathering- When a rock is broken down and NO new products are created. (a physical change) Examples of physical weathering- Frost wedging, Root wedging, Mud cracks, abrasion, sandblasting Chemical Weathering- When a rock is broken down and during that process the mineral content of the rock changes. New products are formed. Elements can be taken out or put in. (a chemical change) Examples of chemical weathering- Acid Rain breaking down rocks, Rust/Oxidation

What is q common rock rule?

Generally If a rock is bigger and more angular (straight/geometric lines) it is closer to its source (Where it originally came from) and younger. If a rock is smaller and more round, smooth it is farther from its source and probably has been around longer.

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ventifact

weirdly shaped rocks formed by sandblasting

V shaped valley

Valley formed by running water

U shaped Valley

Valley formed by ice

How do glaciers form?

Glaciers form when snow turns to firn. What is firn? Firn= layers of snow on the upper part of a glacier that compacts together. Beneath the firn, where it's colder and there's more pressure the firn comes together as thick ice.

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What are glacial striations

Glacial Striations- scratches made in the Earth by a glacier’s underside

What are glacial erratics?

A glacial erratic- A giant rock that seems out of place because it was left behind by a glacier.

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What are drumlins?

Drumlins- Little hills that look like an upside down spoon. Caused by a glacier moving over the land.

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What are kettle lakes?

A kettle lake-Glacier leaves behind a giant chunk of ice in the ground. Over many years the ice melts and fills the hole in the ground

What are moraines?

Moraine are a random mess of everything the glacier picked up and spat out during its journey. The rocks and sediment from a moraine are usually all disorganized and many different shapes and sizes (unsorted).

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What is an ice age and what caused it?

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