Tutor profile: Jenny A.

What influences how soils form?

Soil formation is affected by 5 different factors: 1) Parent material - essentially, this is the basic type of rock or material that forms the basis of the soil. Volcanic ash, weathered sandstone, and till left behind by glaciers will all have different chemical compositions and physical considerations that will affect the resulting soil. 2)Climate - Soil will develop differently in arid regions than in the tropics, as climate affects decomposition rate and soil chemistry. 3)Topography - Topography affects erosion and deposition of soil and potential parent material. 4)Organisms - Both micro and macro level organisms affect soil formation, through decomposition, nutrient cycling, and weathering and erosion. 5) Time - Time is a player in the strength of all of the other factors. These 5 factors together affect what kind of soil will form.

What geologic process is going on in the volcanoes of the Pacific Northwest - the Cascades, volcanoes like Mount St. Helens?

The primary geologic process that is going on to form the volcanoes of the Pacific Northwest - and actually all the volcanoes of the 'Ring of Fire' around the Pacific - is subduction. The Earth's crust is broken up into lots of tectonic plates. The plates of the ocean are composed of rocks with lots of iron (mafic) and are relatively dense when compared to the plates of the continents, which are composed of rocks with less iron and more lighter elements like silicon. So, when a continental plate and an oceanic plate run into each other, the oceanic plate will start to move underneath the continental plate. As the oceanic plate descends farther below the surface, any water trapped in it will start to get superheated. This superheated water will rise up through the continental crust above, and melt rock as it goes. The melted rock will be less dense than the surrounding cool rock, causing it to also rise up towards the surface, resulting in volcanoes.

How did the Moon form?

In simple terms, the Moon formed when a "mini planet" smashed into the early Earth. The object itself got basically obliterated, but the impact also threw a whole bunch of the Earth's crust up into space. These crusty pieces of rock floated around and gradually formed together into the object we now know as the moon. The fact that our Earth's crust is predominately made of lighter rocks than the mantle and core explains why the Moon itself is predominately made of these types of lighter rocks.