Stepwise processes: melting → magma; cooling/crystallization → igneous rocks; weathering/erosion → sediments; compaction/cementation → sedimentary rocks; heat & pressure → metamorphic rocks; uplift/exposure or remelting → repeat cycle.
The rock cycle describes how three major rock types transform into one another: 1) Melting and solidification: Deep inside Earth rock melts to form magma; when magma cools and crystallizes it forms igneous rocks. 2) Weathering, erosion and deposition: Igneous (or any) rocks exposed at the surface are broken down by weathering and transported by erosion; the deposited material forms sediments. 3) Lithification: Sediments are compacted and cemented to form sedimentary rocks. 4) Metamorphism: Igneous or sedimentary rocks buried deep are subjected to high heat and pressure and change into metamorphic rocks. 5) Remelting or uplift: Metamorphic rocks may melt back into magma or be uplifted and exposed to surface processes, continuing the cycle.
- a. epicentre
- b. focus
- c. seismic wave
- d. magnitude
The focus (also called hypocentre) is the point inside the Earth where an earthquake originates. The epicentre is the point on the surface directly above the focus.
b
- a. i, ii & iii are right
- b. i & ii are right
- c. i & iii are right
- d. only I is right
Only (i) is correct. Textbook (page 171) lists Mt. Fujiyama (Mount Fuji) as an example of a dormant volcano. Mt. Kilimanjaro (Tanzania) is given in the book as an example of an extinct/dead volcano, not dormant; the phrase 'Mt. Tanzania' is a mis‑statement (Tanzania is a country). Therefore only statement (i) is true.
d
- a. Statements & reason are true
- b. Statement is true, reason is false
- c. Statement is false, reason is true
- d. Statement & reason are false
Both statements are true. Magma can erupt to the surface when it finds conduits or vents. The interior of the Earth contains hot molten rock (magma) under pressure; this pressure helps drive magma upward through vents.
a
- a. crust
- b. mantle
- c. core
- d. None of the above
Magma is molten rock found mainly in the upper mantle and lower crust; it originates from partial melting of mantle and lower crustal rocks.
b
- a. hydel
- b. thermal
- c. wave
- d. tidal
Thermal energy from Earth's interior (mantle convection due to heat) drives the movement of tectonic plates.
b
- a. north
- b. south
- c. east
- d. west
The landmass (including the Indian plate) of Gondwanaland moved northwards during plate drift, leading to the collision with Laurasia and the formation of mountain ranges.
a
- a. Gondwana
- b. Laurasia
- c. Panthalasa
- d. Pangea
India was part of the southern supercontinent Gondwana before it drifted northward.
a
- a. fold
- b. fault
- c. mountain
- d. earthquake
Stress and tension that stretch rocks causing cracks result in faults (breaks along which movement occurs).
b
- a. crater
- b. vent
- c. chamber
- d. volcanic cone
A crater is the bowl-shaped depression at the summit of a volcano. A vent is the opening through which material is expelled.
a
1 (Endogenetic process) → Volcanic boundaries (endogenetic or internal processes like volcanism occur at such boundaries). 2 (Mantle) → SIMA (SIMA refers to silica–magnesium composition associated with oceanic crust/upper mantle). 3 (Convergent) → Subduction Zone (convergent plate margins cause subduction). 4 (Earthquake) → Seismograph (instrument used to record earthquakes). 5 (Composite volcano) → Pacific Ocean (many composite volcanoes occur around the Pacific 'Ring of Fire').
| # | Correct match |
|---|---|
| 1 | Volcanic boundaries |
| 2 | SIMA |
| 3 | Subduction Zone |
| 4 | Seismograph |
| 5 | Pacific Ocean |
Short definitions: lithosphere (rocks/land), hydrosphere (water bodies), atmosphere (air envelope), biosphere (living organisms). These spheres interact to shape Earth's environment.
Earth is divided into spheres: 1) Lithosphere — the solid outer layer (crust and uppermost mantle) that supports landforms. 2) Hydrosphere — all water on Earth (oceans, rivers, lakes, groundwater). 3) Atmosphere — the layer of gases surrounding Earth, responsible for weather and climate. 4) Biosphere — zone of life where organisms exist, overlapping the lithosphere, hydrosphere and atmosphere.
Density difference: SIAL has lower density (rich in silica and aluminium) while SIMA is denser (rich in magnesium and iron), so the lighter SIAL floats on the denser SIMA.
SIAL (silica + aluminium-rich continental crust) floats over SIMA (silica + magnesium-rich denser layer) because SIAL rocks are less dense than SIMA; buoyancy causes the lighter continental crust to 'ride' above the denser material.
Key contrasting points—location, composition, physical state, thickness, temperature and density.
Core vs Crust: 1) Location: Core is the central innermost part of Earth; crust is the outermost thin layer. 2) Composition: Core is mainly iron and nickel; crust is rich in silica and aluminium (continental) or basaltic rocks (oceanic). 3) State: Outer core is liquid, inner core is solid; crust is solid rock. 4) Thickness: Core extends to ~3,485 km radius; crust averages 5–70 km thick. 5) Density & temperature: Core is much hotter and denser than crust.
Layered model: crust → mantle → outer core (liquid) → inner core (solid); mention thickness, composition and key properties (e.g., mantle convection, magnetic field from outer core).
Earth's structure (from surface to centre): 1) Crust: thin outer layer (continental crust ~30–70 km, oceanic ~5–10 km) composed of lighter silicate rocks. 2) Mantle: extends to ~2,900 km depth, composed of silicate minerals richer in magnesium and iron; includes upper mantle (lithosphere and asthenosphere) where convection occurs. 3) Outer core: liquid layer of iron–nickel alloy (~2,900–5,150 km depth) whose motion generates Earth's magnetic field. 4) Inner core: solid iron–nickel centre (~5,150–6,371 km radius) at very high temperature and pressure. Additionally, the lithosphere (crust + uppermost mantle) is rigid and broken into tectonic plates.
Internal processes build or modify the crust from within (create mountains, volcanoes), external processes wear down and reshape the surface (erosion, deposition). Both interact to form landscapes.
Internal (endogenetic) processes originate within Earth and include volcanic activity, earthquakes, folding and mountain-building caused by plate tectonics and mantle convection. External (exogenetic) processes operate at Earth's surface and include weathering, erosion, transportation and deposition by wind, water, ice and gravity, which shape landforms over time.
Igneous rocks are the first-formed crystalline rocks from magma; subsequent processes transform them into other rock types, so they are considered the 'parent' of many rocks.
Igneous rocks are called primary or mother rocks because they form by the solidification of molten magma and are the original rocks from which other rocks (sedimentary and metamorphic) are derived through weathering, erosion, deposition and metamorphism.
Hypocentre = origin point underground; Epicentre = surface projection of the hypocentre; epicentre typically reported in earthquake locations.
Hypocentre (focus) is the point inside Earth where the earthquake originates. Epicentre is the point on Earth's surface directly above the hypocentre. Hypocentre has depth; epicentre is surface location and usually experiences strongest surface effects.
List and briefly note composition/state: crust (solid), mantle (solid but convective), outer core (liquid iron–nickel), inner core (solid iron–nickel).
Main layers: Crust (continental and oceanic), Mantle (upper and lower mantle), Outer core (liquid), Inner core (solid). Additional divisions: lithosphere and asthenosphere within the upper mantle.
Definitions and examples: active (e.g., Kilauea), dormant (e.g., some definitions list Mount Fuji), extinct (e.g., some ancient volcanoes).
Based on periodicity volcanoes are classified as: 1) Active — currently erupting or likely to erupt in near future. 2) Dormant — not currently erupting but may erupt again (shows signs of activity or has erupted in recent geological times). 3) Extinct — no longer expected to erupt (no magmatic activity and long period of inactivity).
Divergent — relative motion: apart; process: upwelling magma creates new lithosphere; examples: Mid-Atlantic Ridge. Convergent — relative motion: toward; process: subduction or continental collision leads to melting, uplift and deformation; examples: Andes (ocean–continental), Himalayas (continental–continental).
Divergent boundaries: plates move apart; new crust forms at mid-ocean ridges; features — rift valleys, mid-ocean ridges, volcanic activity mainly effusive; earthquakes shallow and less intense. Convergent boundaries: plates move toward each other; one plate may subduct or both crumple; features — deep ocean trenches, volcanic arcs, mountain ranges; earthquakes can be deep and very powerful.
Concise definition with cause and effects: lithospheric plates float and move on the asthenosphere; boundaries of plates explain major geological phenomena.
Plate tectonics is the theory that Earth's lithosphere is divided into rigid plates that move relative to each other over the ductile asthenosphere, driven by forces such as mantle convection, ridge push and slab pull; their interactions produce earthquakes, volcanoes, mountain building and ocean basins.
Characteristics: very long wavelength and high speed in deep water; wave height increases dramatically in shallow water causing coastal inundation and destruction.
A tsunami is a series of large sea waves generated by sudden displacement of a large volume of water — commonly caused by undersea earthquakes, submarine landslides or volcanic eruptions.
P-waves: particle motion parallel to propagation, little structural damage but first arrival. S-waves: particle motion perpendicular to propagation, cannot travel through liquid outer core, contribute to major earthquake damage.
Primary (P) waves: longitudinal (compressional) body waves, fastest, arrive first, travel through solids, liquids and gases. Secondary (S) waves: transverse (shear) body waves, slower than P waves, arrive second, travel only through solids, typically cause larger ground shaking.
List of major positive and negative impacts: immediate hazards (lava, ash, gases), long-term effects (soil fertility, landscape changes, economic benefits like geothermal power).
Volcanic effects: destructive — lava flows, pyroclastic flows, ashfall, volcanic gases, loss of life, property damage, climate cooling from aerosols. Beneficial — formation of fertile soils, creation of new land, mineral deposits, geothermal energy and tourism.
Define volcano then list internal and surface parts: magma chamber (source), conduit/pipe (path), vent/crater (surface outlets), lava and pyroclast deposits forming cones and flows.
A volcano is an opening in Earth's crust through which magma, gases and ash erupt onto the surface. Major components: magma chamber, conduit (pipe), vent, crater, lava flows, pyroclastic cone (cinder cone), ash cloud, and sometimes a caldera.
Contrast in lava viscosity, shape, eruption style and size: shield = fluid lava, wide/low profile; dome = viscous lava, steep/compact.
Shield volcano: broad, gently sloping cone formed by low-viscosity basaltic lava that travels far; eruptions usually effusive (example: Mauna Loa). Volcanic dome: small, steep-sided mound formed by very viscous lava that piles up near the vent; eruptions often explosive and slow (example: lava domes formed after some eruptions of Mount St. Helens).
Mention elastic-rebound theory: strain builds up until rocks break and rebound to a new position; focus (hypocentre) is the rupture point below ground and epicentre is the point on the surface above it.
An earthquake is the shaking of Earth's surface caused by a sudden release of energy in the crust. It occurs when accumulated stress on a fault exceeds the strength of rocks, causing a sudden slip (rupture) and release of elastic energy as seismic waves.
Body waves travel through Earth's interior (P fastest, S slower). Surface waves travel along Earth's surface and usually cause the greatest damage due to larger amplitudes.
Seismic waves are energy waves generated by earthquakes that travel through Earth. Types: body waves — P (primary, compressional) and S (secondary, shear); surface waves — Love waves (horizontal shear) and Rayleigh waves (rolling, vertical and horizontal motion).
Explain cause (plate subduction and convergent boundaries), distribution (circum-Pacific), and effects (high seismicity and volcanism; many major historic earthquakes and eruptions occur here).
The Pacific Ring of Fire is a horseshoe-shaped zone around the margins of the Pacific Ocean characterized by frequent earthquakes and numerous active volcanoes, formed mainly by subduction of oceanic plates beneath continental or other oceanic plates (countries: Japan, Indonesia, Philippines, Papua New Guinea, western coasts of North and South America).
Give clear map markings: a) Pacific Ring of Fire — outline all major subduction and volcanic arcs around Pacific margins. b) Earthquake zones — e.g., Himalayan collision zone and the Chile–Peru subduction zone. c) Active volcanoes — mark coordinates/locations for Mount Fuji (Japan) and Kilauea or Krakatoa (Indonesia). d) Himalayas — draw arc from NW India to NE India; Alps — draw in central Europe. e) Rift valley — draw the Great Rift from Afar Triangle downwards through East Africa.
a. Trace a continuous arc along the margins of the Pacific Ocean (from New Zealand → eastern Australia? actually Tonga/Kermadec → Japan → Aleutians → Alaska → west coasts of Canada/USA → Central America → Andes → back to Southern Chile and islands). b. Earthquake-prone zones (two examples): Himalayan belt (Pakistan → India → Nepal → Bhutan) and west coast of South America (Peru–Chile trench). c. Two active volcanoes: Mount Fuji (Japan) and Kilauea (Hawaii, USA) — mark their locations. d. Himalayas: mark across northern India into Nepal, Bhutan and Pakistan; Alps: mark across central Europe (France–Switzerland–Italy–Austria). e. East African Rift Valley: mark the rift from the Red Sea region through Ethiopia, Kenya, Tanzania down to Mozambique.
Practical role: stay calm, protect yourself first, then help others, ensure safe evacuation if needed, cut utilities if dangerous, call emergency services when necessary and provide accurate information. Prepare a basic emergency kit and a family emergency plan in advance.
Do's: Drop, Cover and Hold On; move to open space away from buildings, trees and power lines after shaking stops; switch off gas, electricity and turn off open flames; help injured and administer first aid; follow official instructions and evacuation routes; assist vulnerable people (children, elderly). Don'ts: Do not use elevators during/after tremors; do not run outdoors during shaking (avoid falling debris); do not light matches or turn on electrical switches if gas leak suspected; do not stand under doorways or near windows, glass or heavy furniture; avoid crowding exits and spreading unverified rumours.