Weathering breaks rocks apart and then erosion takes them away to be transported further by rivers or the ocean, but eventually deposition occurs once its energy has been depleted and material deposits into its new place of deposition.
Geologists use sediment classification to understand erosion and transport processes. For instance, rivers that have lost energy will likely deposit boulders, pebbles, and fine silt.
Weathering
Weathering is the chemical and mechanical breakdown of exposed rocks. Chemical weathering involves altering minerals within rocks to make them softer and more brittle while physical weathering physically fractures rocks into smaller pieces. Erosion is the process by which these softened materials move away from their source – typically by gravity, water flow, wind currents or even ice movement.
Weathering depends on temperature changes, expansion and contraction of rock masses, crack freezing/thawing cycles in rock cracks, stress/pressure exerted upon them from surrounding materials or plant roots penetrating through them, and overlying material. Minerals buried under sediment will break down more slowly.
Minerals found within igneous rocks vary in their susceptibility to weathering. Minerals that rank higher on Bowen’s Reaction Series, like quartz, will break down more slowly than those lower down such as olivine and pyroxene; biological weathering can hasten this process by producing acids which aid in dissolving rocks more quickly.
Erosion
Erosion is a natural process that removes weathered rock material from one place and transports it elsewhere, caused by various agents such as wind, water, gravity (see Chapter 10), or even glaciers. Water erosion typically takes the form of flooding or over time such as when creating stream beds.
Gravity can create erosion by pulling rocks and sediments downhill from mountains or cliffs, as in a landslide or by waves washing pebbles onto beaches. Erosion also plays an integral part in creating distinctive geological features like Utah’s Bryce Canyon and Goblin Valley State Parks’ unique hoodoo formations: rock layers that resist erosion remain standing after less resistant rocks have eroded away, thus leaving behind distinctive hoodoo shapes which define them.
Sublimation
Sublimation, also known as phase transitioning, refers to the process by which solid matter transforms directly from its solid state into gaseous state without passing through liquid stage. It occurs under specific temperature and pressure conditions. Frozen carbon dioxide (dry ice) sublimates at atmospheric temperature; you can witness its transformation when frost forms on windows on cold mornings or stepping outside on snowy days.
Sublimation occurs when solid particles lose enough energy to bond together and transition directly from liquid state into solid form, bypassing liquid altogether. Once completed, this resultant solid is then deposited at its intended site.
Chemical analysis uses the same process that dye-sublimation printers utilize; mass spectrometry systems detect both water molecules and any significant chloro-p-quinodimethane peaks in deposited material for testing purposes.
Lithification
Lithification is the process of turning loose sediment into rock through physical, chemical and mineralogical transformation. Lithification forms part of diagenesis’ larger process that also includes compaction and cementation of sedimentary rocks.
Sandstone is formed through the precipitation of minerals that cement together sand grains – typically quartz, hematite or calcite – in its pores between grains to form strong structures resistant to erosion. This makes sandstone particularly strong and resistant against wear-and-tear.
Organisms can also contribute to lithification by producing minerals in their own pore space. For instance, silica secreting planktonic organisms like radiolaria and diatoms can accumulate on the sea floor and become fossilized into limestone as they buried and recrystallized during lithification; this form of biochemical lithification.