### formation | ridge:

Dune
* Most dunes has spadefoots, which type of toad.
* Some dunes appear to be inactive and covered with dust
  - migrate, pushed by the wind.
  * In physical geography, a 'dune' hill of sand built by eolian processes. Dunes have different forms and sizes based on their interaction with the wind
  - often reach several kilometres in length
* act as a natural barrier and prevent inland flooding.
* also can naturally replenish beaches
  - provide an important natural defence against coastal erosion
* are also the home for many endangered and threatened animals and plants
  - an important part of our coastline
  - asymmetrical in cross section
  - books
  - common on Mars and in the equatorial regions of Titan
  - essentially terrestrial systems in which wind-driven sand transport is of key importance
  - formed by sand being blown up onto the beach by onshore winds
  - hills of sand formed by wind blowing over the beach
  - important for gathering and keeping sand together
  - landforms on the desert that are shaped by the winds
  - most likely to form where winds are strong and generally blow from the same direction
  - mounds or ridges of wind-deposited sand
  - of two types - linear and parabolic
  - rare in North American deserts, and fluvial processes dominate much of the landscapes
  - subject to a high degree of erosion because they lie directly in the path of the tides
* are the front line of defense from wind, water, tropical storms and hurricanes
  - natural barrier that dissipates all the wave strength
  - obvious depositional forms and range enormously in form, size and composition
  - transport limited only during summer
  - unstable - subject to the ravages of wind and water
  - vulnerable to trampling, vehicles, dumping of refuse, grazing, and littering
* associated with beaches are hills or ridges of sand that have been shaped by the wind.
* can migrate at a rate of several metres a year
  - roll over trees and buildings, or be washed away by storms
* constantly change if there is nothing to prevent the wind from moving the sand around.
* depend on plant growth such as dune grass for their stability.
* dominated by Asiatic sand sedge are also more vulnerable to wind blowouts and storm erosion.
* drift like leaves.
* form typically on large flat beach profiles with a large sediment supply to the backshore.
* formed in multi-directional wind regimes are rare and, when seen, generally small.
* generally form parallel to the backbeach or a dune fields shoreward from ebb deltas at inlets.
  - regular and irregular forms
* increase in size inland.
* migrate constantly with the wind.
* move grain by grain while the wind whistles around the tenacious flora surviving in the sands.
* occur at the landward extreme of sandy beaches
  - in different shapes and sizes, formed by interaction with the flow of air or water
  - on grazed land, ungrazed land and on private agricultural land
  - when dry sand begins to build at some obstacle, such as plant debris or a shell
* occur, for example, in some deserts and along some coasts.
* produce cross-bedding in deposited sediment.
* protect against storm tides
  - inland areas from wind and wave action and help to preserve the shore
  - shorelines from erosion and property damage caused by storm waves
* provide habitats
  - privacy and shelter from the wind
* run parallel due to the wave properties of the air.
* stabilize the mounds of sand that protect the coast against winds and pounding tides.
* tend to form in topographic pockets where the sand is confined
  - on flat surfaces
* typically contain granular fragments of rocks and minerals.

### formation | ridge | dune:

Coastal dune
* Many coastal dunes are transverse.
* are the product of wind-deposited sand anchored by sparse mats of vegetation.
* have a tendency to become vegetated.