Geology Weathering Overview

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Questions and Answers

What best describes mechanical weathering?

Decomposition of materials influenced by water and oxygen.

Breakdown of rocks through chemical reactions.

Physical processes that reduce rocks to smaller pieces. (correct)

Weathering caused solely by living organisms.

Which of the following is an example of frost weathering?

Water freezing in cracks and expanding to widen them. (correct)

Rocks expanding and contracting with temperature changes.

Minerals crystallizing after water evaporates.

The outer layer of rock peeling away due to reduced pressure.

What is a key factor affecting the rate of chemical weathering?

The presence of certain geological agents. (correct)

The color of the rock.

The age of the rock formation.

The hardness of the rock alone.

Which process describes the phenomenon of crystals pushing into cracks in rock?

Salt Crystal Growth Signup and view all the answers

How do warm and cold climates affect chemical weathering?

They produce different types of chemical processes. Signup and view all the answers

What type of minerals in rocks tends to weather more quickly when exposed to environmental elements?

Minerals that are most reactive with water and oxygen Signup and view all the answers

Which of the following climatic conditions is likely to experience the highest rate of weathering?

Warm and humid climates Signup and view all the answers

What practice is recommended to reduce soil erosion in agricultural fields?

Planting cover crops Signup and view all the answers

What is the primary characteristic of mass wasting processes?

They involve the movement of materials downslope due to gravity Signup and view all the answers

Which type of mass wasting involves a rapid, destructive movement of rock and is often referred to as a rock avalanche?

Rockslide Signup and view all the answers

What primarily causes runoff in the water cycle?

Non-porous surfaces and saturated ground Signup and view all the answers

What role does vegetation play in preventing mass wasting?

It anchors soil through roots. Signup and view all the answers

Which phase change is responsible for water returning to the Earth's surface as precipitation?

Condensation Signup and view all the answers

How do infiltration and runoff differ in the water cycle?

Infiltration involves water seeping into soil; runoff involves water flowing across the surface. Signup and view all the answers

Which type of mass wasting involves a coherent block sliding down a curved surface?

Slump Signup and view all the answers

What is a key factor influencing the occurrence of mass-wasting events?

Lack of vegetation Signup and view all the answers

What percentage of Earth's water is freshwater and what portion of that is accessible for use?

3%; less than 1% Signup and view all the answers

How do normal faults form during tectonic activity?

When two blocks of rock move away from each other. Signup and view all the answers

What term describes the land area where precipitation drains into a common waterway?

Drainage basin Signup and view all the answers

What classification differentiates a reverse fault from a normal fault?

The direction of rock movement. Signup and view all the answers

What factor increases the rate of infiltration in soil?

High permeability of the soil Signup and view all the answers

What is the primary method by which water is returned to the atmosphere from the surface of the Earth?

Transpiration Signup and view all the answers

Which type of geological fold has older rocks at its center?

Anticline Signup and view all the answers

What is an earthflow?

A flow of fine-grained material. Signup and view all the answers

What major geological event is directly associated with the formation of mountains?

Plate tectonics and orogeny Signup and view all the answers

Study Notes

Weathering and Its Types

Weathering breaks down rocks on Earth's surface, occurs via mechanical and chemical processes.
Mechanical Weathering: Physical breakdown of rocks into smaller pieces, includes:
- Thermal Expansion: Rocks expand and contract with temperature changes.
- Frost Weathering (Ice Wedging): Water freezes in rock cracks, expanding and enlarging them.
- Exfoliation: Outer layers of rocks peel off as pressure decreases when rocks reach the surface.
- Abrasion: Rock fragments collide and wear against each other, driven by natural forces.
- Salt Crystal Growth: Evaporated water leaves behind salt crystals that expand in cracks, causing further weathering.
Biological Weathering: Conducted by living organisms like plants, animals, fungi, contributing to mechanical and chemical weathering.

Chemical Weathering

Involves transformative chemical processes such as acidification, hydrolysis, carbonation, and oxidation.
Consists of two phases: decompose original materials and form new secondary materials.
Rate of chemical weathering influenced by:
- Material hardness: Harder materials weather more slowly.
- Environmental conditions: Climate, moisture, and the presence of geological agents like water and oxygen enhance chemical reactions.

Soil Formation and Composition

Soil is an essential medium comprising sediments, minerals, organic matter, gases, and microorganisms.
Develops slowly through weathering, erosion, and deposition, often starting with pioneer species adding organic material.
Soil types categorized by grain size (sand, silt, clay) and structure (granular, platy, columnar), with granular soil ideal for crops.

Soil Erosion Causes and Prevention

Soil erosion occurs due to wind, water, or gravity, exacerbated by exposed or tilled land.
Loss of topsoil leads to reduced nutrient quality and crop yields, alongside potential water pollution from runoff.
USDA promotes erosion prevention practices such as shelterbelts, no-till farming, cover cropping, and contour farming, which stabilize soil.

Mass Wasting

Defined as the downward movement of rock and soil due to gravity, influenced by water saturation and seismic activity.
Types of mass wasting include slumps, rockslides, debris flows, and earthflows.
Slumps: Slow downslope movement of semi-consolidated material.
Rockslides: Rapid, destructive downward movement of rock material.
Debris Flow: Highly saturated mass of soil and various rock sizes moving fluidly.
Creep: Gradual downslope movement of soil, often observable in tree trunk bending.

Mass Wasting Triggers and Consequences

Mass wasting caused by factors like increased rainfall, loss of vegetation, earthquakes, and steep slopes.
Direct impacts include property damage and loss of life; indirect effects involve economic repercussions and reduced tourism.

Geological Structures and Processes

Folds: Result from compressive stress, classified as anticlines (upward folds), synclines (downward folds), and monoclines (single limb).
Faults: Fractures in the Earth's crust where movement occurs; classified into normal, reverse, and strike-slip faults based on their movement patterns.

Mountain Formation (Orogeny)

Mountains, characterized by elevation and rock composition, arise from tectonic activities.
Types include fold mountains (formed by plate collisions), dome mountains (magma pushing upward), and hotspot mountains (like those in Hawaii).

The Water Cycle

The water cycle involves processes like evaporation, condensation, precipitation, runoff, and infiltration.
Key phases include:
- Evaporation: Liquid water transforms into vapor.
- Condensation: Water vapor cools to form clouds.
- Precipitation: Water returns to the ground as rain, snow, or sleet.
Infiltration involves water seeping into soil, critical for groundwater replenishment.

Global Water Distribution

Water on Earth is predominantly salty, with only 3% as freshwater, most of which is in the form of glaciers and underground reserves.
Surface water constitutes only a small portion of available freshwater.

Drainage Basins

Drainage basins (or watersheds) direct precipitation and spring water to a common outlet, varying greatly in size.
High ground surrounding these basins acts as divides, separating water flow into distinct drainage systems.### Drainage Basin Systems
Drainage basins slope into river systems, collecting runoff from precipitation.
Rivers begin with runoff which flows across surfaces, growing as they move downhill.
First-order streams are the smallest, originating from small areas without tributaries.
River systems evolve as first-order streams merge into second-order streams and larger.
A drainage basin can comprise multiple smaller basins, all contributing water to a river.
The Mississippi River drainage basin spans 31 U.S. states, draining into the Gulf of Mexico.

Streamflow Dynamics

Streamflow describes water movement in a channel, influenced by water source, speed, and obstacles.
Water can flow in two ways: laminar (quiet, smooth flow) or turbulent (chaotic, loud flow).
Laminar flow features parallel layers with slow velocities and can be unidirectional, pulsatile, or oscillatory.
Turbulent flow involves collisions with barriers, mixing water particles, and is typified by white-water rafting environments.

Erosion and Geological Processes

Weathering breaks down large rocks into smaller fragments via wind, water, and glaciers.
Erosion transports these fragments, with water erosion being faster compared to wind or glacial.
Deposition involves the accumulation of eroded materials in new locations, altering landscapes.
All three processes (weathering, erosion, and deposition) continuously shape landforms over time.

Geology Principle: Uniformitarianism

Uniformitarianism posits the present explains the past, guiding geological event analysis.
Four key principles help understand landform progression:
- Law of original horizontality
- Law of superposition
- Crosscutting relations
- Unconformities

Stream Valley Formation

Stream valleys develop as water flows at the lowest terrain point, shaped by erosion.
The aging process of valleys includes:
- Youth stage: steep gradient and V-shaped valley.
- Maturity stage: gentler gradient, U-shaped valley, and floodplain formation.
- Old age stage: wide, flat, slow-moving waterway with low gradient.

Base Level of Streams

Base level marks the lowest erosion point for running water, including ultimate (sea level) and local (like lakes) types.
Base level influences erosion and sediment deposition, affecting stream dynamics.

Bedrock and Bedrock Channels

Bedrock is a solid rock foundation often covered by loose soil and sediments (alluvium).
Erosion processes create bedrock channels through abrasion and plucking (quarrying) of rocks.

Alluvial Channels and Features

Alluvial channels change shape based on water flow and sediment dynamics, leading to:
- Meandering streams: winding paths formed by point bar deposits.
- Braided streams: interwoven channels with sediment bars.
- Straight and sinuous channels: display linearity but vary in water flow due to sand bar deposition.
- Anastomosing channels: interconnected streams forming networks.
Geological features from alluvial channels include oxbow lakes, flood plains, natural levees, and terraces.

Groundwater Dynamics

Groundwater flows through natural fissures in the Earth, influenced by porosity, permeability, and gravity.
Porosity determines soil's water retention ability, while permeability and gravity regulate flow speed.

Aquifers

Aquifers are subsurface reservoirs of water, classified as confined (trapped by impermeable layers) or unconfined (free to flow).
Natural springs form when aquifer water finds exit points, resulting in various surface water bodies.
The quality of spring water varies based on environmental factors, impacting its suitability for consumption.

Well Types and Function

Wells have been used for over 8,000 years to access underground water resources.
Types of wells include:
- Dug wells: shallow, manually excavated.
- Driven wells: tubes propelled into the ground to reach aquifers.
- Drilled wells: deep wells created using machinery, often over 1,000 feet.
Artesian wells utilize pressure to push water to the surface, minimizing the need for pumps.

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Description

This quiz focuses on the process of mechanical weathering, which involves the physical breakdown of rocks into smaller fragments. Through examples such as thermal expansion and frost weathering, you will learn how temperature changes and water influence the weathering process. Test your understanding of these concepts and their impact on Earth's surface.