positive estuaries

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4 types

fjord: fjords are drowned river valleys that were cut by glaciers when the sea level was lower. they are steep -sided, with deep water. can be surrounded by snowed on mountains. may have a shallow sill near the the mouth that was formed by sediment deposited at the lower end of the glacier as it flowed through the valley. they are common on the norwegian coast, new zealand and south alaska. have a moderately high input of freshwater!

bar built: formed when the sandbar is parallel to the coastline by wave action and longshore drift. have a shallow lagoon. typically the rivers have low water volume through out the year. the bar of the estuary prevents wave impact causing destruction/ damage. there are some located in carolina.

tectonic: were formed when a section of land drops below sea level as a result of vertical movement along a fault. are located on coasts where there're subduction zones or transform plate boundaries. an example is san fran bay

coastal plain: formed when sea levels rose from melting ice at the end of the last ice age. generally called drowned river valleys. ar popular on passive margins for example the east coast of the usa. depth of water increases closer the mouth. they are common worldwide.