A horizon

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soil profiles on hillslopes

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Ice Sledge Hockey, Hockey Canada Cup, USA (left) vs Canada, 2009. UBC Thunderbird Arena, Vancouver, BC, competition site for Olympic ice hockey and Paralympic ice sledge hockey. Vancouver 2010 Olympic and Paralympic Winter Games, Vancouver Olympics

10 Best Hockey Players of All Time

The Prado Museum facade at the Diego Velaszquez memorial. Established in 1819, the museum is considered the best collection of Spanish art and one of the world's finest collections of European art. Madrid, Spain

20 Paintings You Have to Visit at the Museo del Prado in Madrid

Town of Sisimiut located on the coast of the Davis Strait on Kangerluarsunnguaq Bay, Greenland

The Largest Islands in the World

Four year old boy with grandfather and father lighting Hanukkah menorah. Photo taken on: December 21st, 2009

Which Is Correct: Hanukkah or Chanukah?

Srinivasa Ramanujan, Indian mathematician and autodidact.

6 Interesting Facts about Srinivasa Ramanujan

Entrants falling and tumbling over while chasing the cheese at the 2016 'Cheese Rolling' held at Cooper's Hill, in the Cotswolds, Brockworth England

7 of the World’s Most Dangerous Festivals

Nativity Scene, Adoration of the Magi, Church of the Birth of the Virgin Mary, Montenegro

Why Is Christmas in December?

A horizon

soil type

Learn about this topic in these articles:

composition

In soil: Soil horizons
…surface litter) is termed the A horizon. This is a weathered layer that contains an accumulation of humus (decomposed, dark-coloured, carbon-rich matter) and microbial biomass that is mixed with small-grained minerals to form aggregate structures.
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passage of time

In soil: Time
…the humus content of the A horizon, which, for soils less than 10,000 years old, increases continually at a rate dependent on parent material, vegetation, and climate. Typically, this rate of increase slows after about 10,000 years, plant nutrients begin to leach away, and a significant decline in humus content…
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