Topographic Maps and Landscape Processes Notes

Topographic Maps

  • Definition: Maps that represent the elevation and shape of the land using contour lines.

Key Features of Topographic Maps

  • North Arrow: Indicates true north direction in relation to the map.
  • Magnetic Declination: The angle between true north and magnetic north, affects navigation accuracy.
  • Map Scale: Essential for interpreting distances on a map.
  • Fractional Scale: A ratio (e.g., 1:24,000) representing map distance to actual distance.
  • Graphical Scale: A visual representation of scale, usually as a bar.
  • Longitude & Latitude: A coordinate system for pinpointing locations.
  • Longitude: Lines running north-south.
  • Latitude: Lines running east-west.
  • Township-Range-Section: A system dividing land into squares for surveying.
  • Equator & Prime Meridian: Define the geographical coordinate system; Equator at 0° latitude, Prime Meridian at 0° longitude.
  • Parallels: Lines of latitude that run parallel to each other.
  • 7.5 Min Quadrangle: A type of topographic map covering a specific area (7.5’ of latitude and longitude).

Contour Lines and Analysis

  • Contour Interval: Vertical distance between contour lines, indicates elevation change.
  • Index Contour: Thicker contour lines labeled with elevation values for easier navigation.
  • Law of V’s / Streams: Contour lines form a ‘V’ shape crossing streams, with V pointing upstream.

Landscape Analysis Criteria

  1. Landform: The shape of Earth's surface (mountain, valley, etc.).
  2. Material: Types of rocks or sediments present in an area.
  3. Age: Relative or absolute age of the landform.
  4. Process: Geophysical forces (e.g., erosion, deposition) that formed the land.

Soil and Mass Wasting

Bedrock vs. Regolith

  • Bedrock: Solid rock beneath soil.
  • Regolith: Loose rock and soil overlaying bedrock.

Types of Material

  • Colluvium: Material moved by gravity, typically found at the base of slopes.
  • Alluvium: Sediments deposited by running water.
  • Drift: Glacial deposits, including till and outwash.
  • Lacustrine: Sediments from lake environments.
  • Anthropogenic: Landforms made by human activities.

Mass Wasting Types

  1. Creep: Slow movement of soil downhill.
  2. Slide: Rapid movement along a surface.
  3. Flow: Material movement resembling fluid motion.
  4. Debris Flow: A saturated landslide of water, soil, and rock.
  5. Mudflow: Fast movement of fine sediment and water.
  6. Landslide: Rapid downhill motion of rock or soil.
  7. Rock Fall: Free-fall of rock from steep slopes.
  8. Solifluction: Slow soil movement in cold regions.
  9. Slump: Rotational movement of earth down a slope.

Rivers and Fluvial Processes

  • Channel: The main path of a river’s flow.
  • Floodplain: Flat land adjacent to a river that floods during heavy rains.
  • Terrace: Step-like landforms indicating previous river levels.
  • Flood Discharge: Increased water flow during floods.
  • Normal Discharge: Average flow in a river.

River Types

  • Meandering: Rivers with curves and bends.
  • Braided: Rivers with multiple interconnected channels.
  • Oxbow Lake: A lake formed from an abandoned meander.

Water Transport in Rivers

  • Bedload: Heavy particles transported along the riverbed.
  • Suspended Load: Light particles carried within the water column.
  • Dissolved Load: Minerals dissolved in river water.

Drainage Patterns

  • Dendritic: Tree-like branching pattern.
  • Trellis: Parallel streams with right-angle tributaries.
  • Radial: Streams radiating outward from a central point.
  • Watershed: Area draining into a single river system.
  • Drainage Divide: A ridge separating watersheds.

Hydrologic Cycle

  • Processes:
  1. Precipitation: Water comes from the atmosphere as various forms (rain, snow).
  2. Evaporation: Liquid water converted to vapor.
  3. Infiltration: Water filtering into the ground.
  4. Runoff: Water flowing overland to water bodies.
  5. Transpiration: Water expelled from plants into the atmosphere.

Key Water Storage Types

  • Soil Moisture: Water held in soil.
  • Groundwater: Water below Earth’s surface.
  • Surface Water: Found in lakes and rivers.

Glacial Processes and Landforms

Glaciers Basics

  • Types of Glaciers:
  • Alpine: Found in mountainous areas.
  • Continental: Large ice sheets such as Antarctica.
  • Glacial Ice Formation: Snow compresses into firn, then ice.
  • Movement: Driven by gravity through basal slip and internal flow.

Erosional Effects

  • Plucking and Abrasion: Processes where glaciers erode landscapes.
  • Striations: Marks on bedrock caused by glaciers.
  • U-shaped Valleys: Formed by glacial carving compared to V-shaped valleys carved by rivers.

Depositional Features

  • Moraines: Accumulation of debris pushed by glaciers.
  • Drumlins: Hills formed by glacier movement.
  • Kettles: Depressions formed by melting ice blocks.

Coastal Geomorphology

  • Coast vs. Ocean: Coasts are land areas adjacent to oceans.
  • Tides: Caused by gravitational pull, including spring and neap tides.
  • Erosional vs. Depositional Coasts:
  • Erosional: Features like cliffs and sea stacks.
  • Depositional: Beaches, bars, and coastal wetlands.

Beach Dynamics

  • Longshore Drift: Movement of sand along the shore.
  • Swash and Backwash: Movement of water up and down the beach after waves break.

Summary of Key Concepts

  • Understanding contour lines and their implications for elevation and landscape features is crucial for interpreting topographic maps.
  • A solid grasp of fluvial processes informs how rivers shape landscapes and affects watershed management.
  • Awareness of hydrologic cycles plays a critical role in water resource management and environmental science.
  • Glacier dynamics provide insights into historical climate change and contemporary sea-level issues.
  • Coastal processes are key to understanding landform development and coastal management practices.