How do the three rock types form, and how does the rock cycle turn one into another?
Classify igneous, sedimentary and metamorphic rocks by how they form and explain the rock cycle, including how cooling rate, lithification, and heat and pressure transform rock (Virginia 2018 Earth Science SOL ES.5).
A SOL-level answer on rocks for the Virginia Earth Science EOC: how igneous, sedimentary and metamorphic rocks form, the link between cooling rate and crystal size, clastic versus chemical sediment, foliated versus nonfoliated metamorphic rock, and how the rock cycle transforms one type into another, with worked exam questions.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
Virginia Earth Science SOL standard ES.5 asks you to classify the three rock types by how they form and to explain the rock cycle. The EOC tests this with diagrams of the rock cycle (drag-and-drop the process between rock types), with texture-to-formation reasoning, and with identification from a description. The central skill is connecting a rock's texture and composition to the process that made it.
Igneous rock: cooled from melt
The single most tested igneous idea is crystal size versus cooling rate: big visible crystals mean slow, deep cooling; tiny or no crystals mean fast, surface cooling.
Sedimentary rock: compacted and cemented
Because sedimentary rocks form in layers and preserve fossils, they are central to the geologic time and dating topics later in the course.
Metamorphic rock: changed by heat and pressure
A common EOC pairing is the parent-to-metamorphic link: shale becomes slate, limestone becomes marble, sandstone becomes quartzite, granite becomes gneiss.
The rock cycle
The rock cycle is the model that ties the three types together: matter moves between them through geologic processes, and any rock type can be transformed into any other. The processes are melting (rock to magma), cooling and solidifying (magma to igneous rock), weathering and erosion (rock to sediment), deposition then compaction and cementation (sediment to sedimentary rock), and heat and pressure (rock to metamorphic rock). There is no single fixed path: a sedimentary rock might melt and become igneous, or be metamorphosed, depending on conditions. The energy driving the cycle comes from Earth's internal heat (for melting and metamorphism) and the Sun and gravity (for weathering, erosion and deposition).
Try this
Q1. A rock is made of cemented, rounded pebbles. Which rock type is it, and how did it form? [2]
- Cue. Sedimentary (clastic); fragments were deposited, then compacted and cemented (lithification).
Q2. Explain why basalt has much smaller crystals than granite. [2]
- Cue. Basalt is extrusive (lava cooled quickly at the surface), so crystals had little time to grow; granite is intrusive (magma cooled slowly underground), so crystals grew large.
Exam-style practice questions
Practice questions written in the style of VDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
VA Earth Science SOL 2023 (style)1 marksA rock has large, interlocking crystals you can see without a hand lens. What does this tell you about how it formed? (A) it cooled quickly at Earth's surface. (B) it cooled slowly deep underground. (C) it formed from cemented sand. (D) it formed from heat and pressure on shale.Show worked answer →
A 1-point multiple-choice item linking texture to formation.
The correct answer is B. Large crystals mean slow cooling, which happens deep underground (intrusive igneous rock such as granite), giving crystals time to grow. Quick cooling at the surface (A) makes small crystals or glass (extrusive rock such as basalt). Cemented sand (C) is sedimentary, and heat and pressure on shale (D) makes metamorphic slate.
The test rewards the rule: slow cooling gives large crystals, fast cooling gives small crystals.
VA Earth Science SOL 2024 (style)2 marksA geologic process turns the sedimentary rock shale into the metamorphic rock slate. (a) State the two main factors that cause this change. (b) Describe one way to continue the rock cycle so that the slate becomes an igneous rock.Show worked answer →
A 2-point item on the rock cycle.
(a) 1 point: heat and pressure (without melting) cause metamorphism of shale into slate.
(b) 1 point: if the slate is heated enough to melt, it becomes magma; when that magma cools and solidifies, it forms an igneous rock. (Acceptable alternative path: the slate is uplifted, weathered and eroded into sediment, then buried and lithified, but the direct route to igneous rock is melting then cooling.)
Markers reward heat and pressure in (a) and a valid rock-cycle pathway (melting then cooling) in (b).
Related dot points
- Define a mineral and identify common rock-forming and ore minerals from their physical properties, including hardness, luster, streak, cleavage, color and density (Virginia 2018 Earth Science SOL ES.4).
A SOL-level answer on minerals for the Virginia Earth Science EOC: the five-part definition of a mineral, the physical properties used to identify them (hardness, luster, streak, cleavage and fracture, color, density), the major mineral groups led by the silicates, and why structure-based properties beat color, with worked exam questions.
- Describe the compositional and physical layers of Earth's interior (crust, mantle, outer core, inner core; lithosphere and asthenosphere) and explain how seismic waves provide the evidence (Virginia 2018 Earth Science SOL ES.7).
A SOL-level answer on Earth's interior for the Virginia Earth Science EOC: the crust, mantle, outer core and inner core, the lithosphere and asthenosphere, the difference between continental and oceanic crust, and how P-waves and S-waves and the shadow zone reveal that the outer core is liquid, with worked exam questions.
- Explain plate tectonic theory: the evidence for moving plates, mantle convection as the driving force, the features and motions at divergent, convergent and transform boundaries, and Virginia's geologic provinces (Virginia 2018 Earth Science SOL ES.7).
A SOL-level answer on plate tectonics for the Virginia Earth Science EOC: the evidence from continental fit, fossils and seafloor spreading, mantle convection as the driving force, the features at divergent, convergent and transform boundaries, hot spots, and Virginia's geologic provinces from the Coastal Plain to the Appalachian Plateau, with worked exam questions.
- Distinguish mechanical and chemical weathering, identify the agents of erosion and deposition, and explain how particle size, sorting and water velocity control where sediment is deposited (Virginia 2018 Earth Science SOL ES.6 surface processes).
A SOL-level answer on surface processes for the Virginia Earth Science EOC: mechanical versus chemical weathering and what speeds each, the agents of erosion (water, wind, ice, gravity), how water velocity controls the size of sediment carried and deposited, sediment sorting and rounding, and landforms like deltas and moraines, with worked exam questions.
- Apply the principles of relative dating (superposition, original horizontality, cross-cutting relationships, inclusions and unconformities) to sequence events in a geologic cross section (Virginia 2018 Earth Science SOL ES.9).
A SOL-level answer on relative dating for the Virginia Earth Science EOC: the law of superposition, original horizontality, cross-cutting relationships, inclusions and unconformities, the difference between relative and absolute age, and how to sequence the events in a geologic cross section, with worked exam questions.
Sources & how we know this
- 2018 Science Standards of Learning (Earth Science) — Virginia Department of Education (2018)
- SOL Practice Items (All Subjects) — Virginia Department of Education (2024)