1. Geomorphic Processes: I. Endogenic
I. Volcanic and Tectonic Processes – Eruptions, Earthquakes,
and Landforms

2. Geomorphology – a major subfield of geography
– Study of landforms – their origin and change over time and space
Geomorphic Processes: Physical processes which create and modify landforms on the surface of the earth
Are landform changes
gradual or abrupt?
These processes operate
in episodic manner – with
earthquakes and volcanic
eruptions causing a
punctuated equilibrium

3. Geomorphic Processes:
A. Endogenic
(Endogenous)
B. Exogenic
(Exogenous)
Relates closely to the
Rock Cycle 

4. A. Endogenic Processes
Endogenic Processes are large-scale landform building and transforming processes
– they create relief.
1. Igneous Processes
Volcanism: Volcanic eruptions  Volcanoes
Plutonism: Igneous intrusions
Tectonic Processes (Also called Diastrophism)
Folding: anticlines, synclines, mountains
Faulting: rift valleys, graben, escarpments
Lateral Faulting: strike-slip faults
Earthquakes  evidence of present-day tectonic activity

5. Igneous Processes and Volcanoes

6. Igneous Processes
– involving eruptions or emplacements of molten magma from the earth’s mantle (extrusive and intrusive igneous rocks)
Volcanism : It refers to the extrusion of rock matter from earth’s subsurface to the exterior, and the creation of surface terrain features –
Volcanoes are mountains or hills that form in this way.
How Volcanoes are Formed
About 95% of active volcanoes occur at the plate subduction zones and at the mid-oceanic ridges.
Subduction is a process of plate tectonics where one lithospheric plate is pushed below another.
The other 5% occur in areas associated with lithospheric hot spots.

7. Where are Volcanoes Found?

8. Where are Volcanoes Found?
Convergent Plate Boundaries  Subduction Zones
Oceanic-oceanic  island arcs
Aleutian, Kurile, Marianas, Tonga
Oceanic-continental  active continental margins
South America, North America, Central America, Kamchatka
Divergent Plate Boundaries  Mid-Oceanic Ridges
and Rift Valleys
Continental-Continental  Continental rifts
East Africa, Red Sea-Gulf of Aqaba
Oceanic-Oceanic  Oceanic rifts
Mid-oceanic ridges, spreading sea floors, volcanic islands
Iceland, Azores
Intraplate  “Hotspots” or “Mantle Plumes”
Oceanic islands
Hawaii, Emperor Seamount Chains – Pacific Ocean
Continental
Yellowstone, Wyoming, USA

9. Explosive vs. Effusive, depends mainly on temperature and chemical
A volcano is generally a conical shaped hill or mountain – some active, others dormant.
Built by accumulations of lava flows, and tephra (or fragmented rock material ejected by a volcanic explosion -- also called pyroclastic material, ranging in size from volcanic ash, cinder to volcanic “bombs”
Volcanic eruptions
Explosive vs. Effusive, depends
mainly on temperature and chemical
differences in the magma
 silica-rich felsic magma has greater
potential for explosive eruption
 basalt-based mafic magma leads to
more effusive eruption

10. Volcanic Landforms
Volcanic activity gives rise to such topographic features as:
Lava Flows  ropy pahoehoe, and blocky aa

11. Volcanic Islands
related to hot spots, as in Hawaii
related to divergent plates and seafloor spreading, as in Iceland

12. Volcanic Mountains
 (a) Shield, (b) Cinder Cone, (c) Composite Cone or Stratovolcano
and (d) Plug Dome volcanoes + (e) Caldera

13. SHIELD VOLCANOES
Shield volcanoes are volcanic mountains built up by the eruption of fluid, basaltic lava flowing out of a central vent.
They have broad bases with very gentle slopes
The largest shield volcano on Earth is Mauna Loa in Hawaii which rises from its
base on the seafloor
to a height of 17 km
(10.5 miles).

14. CINDER CONE VOLCANOES
Amboy Crater, southeastern California
A cinder cone is a steep, conical hill of volcanic fragments that accumulate around and downwind from a vent
Cinder cones range in size from tens to hundreds of meters tall.

15. COMPOSITE VOLCANOES or STRATOVOLCANOES
Stratovolcanoes are very tall, 1000s of feet, and are typical cone-shaped mountains
Produced by alternating layers of felsic and mafic magmas, hence stratas  and “Stratovolcano”
Most have snow, ice and even glaciers at top because of their heights
Eruptions are mostly explosive, but often also effusive
Examples: Mt. Shasta, Mt. Hood,
Mt. Rainier, Mt. Fujiyama, Mt. St. Helen

16. Mt. St. Helens a typical composite volcano
(before and after 1980 eruption)

17. PLUG DOME VOLCANOES These volcanoes produce thick pasty lava
The lava cools into angular blocks after it is slowly squeezed out of the vents
Mt. Lassen, northern California

18. Caldera
The most explosive type of volcano is the caldera. The cataclysmic explosion of these volcanoes, and subsequent subsidence, leave a huge circular depression on Earth's surface.
Wizard Island and Crater Lake,
Oregon

19. WORLD’S LARGEST CALDERA
Lake Toba, Indonesia
Largest recognized caldera
Lake Toba, Indonesia
Erupted ~ 75,000 years before present (ybp)
Measures 20 miles by 60 miles
Ejected 2500 km3 of material into atmosphere

20. KRAKATAU CALDERA
INDONESIA

21. Long Valley Caldera California
Lava flows of the Mono-Inyo Craters volcanic chain in Long Valley Caldera, California
The most recent eruptions from this chain occurred about 250 and 600 years ago
Scientists have monitored geologic unrest in the Long Valley, California, area since 1980
The central part of the Long Valley Caldera had begun actively rising
Unrest in the area persists today

22. YELLOWSTONE CALDERA

23. Plutonism:
Igneous intrusions, plutons, are eventually exposed at the surface, and tend to stand higher than surrounding landscape.
Stocks, Batholiths, Laccoliths, Sills, Dikes, and Volcanic Necks.

25. Devil’s Tower, Wyoming: Volcanic Neck
Morro Rock:
Volcanic Necks in California

26. Tectonic Processes and Earthquakes

27. Tectonic Processes – Also called Diastrophism, it relates to:
Tectonic forces, which not only move the lithospheric plates, but also cause bending, warping, folding, tilting, and fracturing of earth’s crust at various scales.
Such deformation
(nature, orientation,
inclination and
arrangement) of
affected rock layers
is recorded in the
rock structure

28. Rock Structure
Near Golden Gate Bridge
San Francisco, CA

29. Relative to adjacent rock masses, the rock layers may also
Relative to adjacent rock masses, the rock layers may also become offset, uplifted, or down-dropped
Orientations of inclined rock layers are measured by their strike (compass direction) and dip (angle)

30. Three Types of Tectonic Force
and associated types of structural deformation

31. Compressional Tectonic Forces
Folding
– anticlines, synclines
– overturn
-- recumbent fold

32. Faulting
– reverse fault
-- thrust fault (overthrust)

33. Tensional Tectonic Forces
Faulting
-- Fault blocks
and Normal faults
– Rift valleys (Rio Grande in NM and CO, East Africa, and Dead Sea)
– Escarpment (scarp) – fault scarps

34. Tilted fault blocks
-- Death Valley, California

35. Graben & Horst Topography
– Basin and Range Region of western U.S.

36. Shearing Tectonic Forces:
Lateral Faulting
– strike-slip fault vs. dip-slip faults
– San Andreas Fault

37. along the Carrizo Plain in central California
San Andreas Fault
along the Carrizo Plain
in central California

38. Earthquakes : Evidence of present-day tectonic activity
What is an Earthquake?
A wave-like sudden vibration or trembling in the Earth – a form of wave energy that travels through the bedrock
Happens when accumulated tectonic stress is relieved through sudden, lurching movement of crustal blocks along a fault line
The motion is caused by quick release
of seismic waves which travels away
from a sub-surface point of sudden energy
release – the Focus
Epicenter is located at the earth’s surface
immediately above the focus

39. Seismic Body Waves are of two types:
Although most earthquakes occur along plate boundaries or fault lines, they can also be triggered by volcanic eruptions or magma beneath the surface. Earthquakes can precede or accompany volcanic eruptions.
Earthquakes shock waves or Seismic Waves travel through the body of the Earth (BODY WAVES) and along the surface (SURFACE WAVES).
Seismic Body Waves are of two types:
P-waves (Primary waves) are faster, traveling at about 5 km/s
These high-frequency, short waves move through solids and liquids
Ground is moved forward and backward as the wave passes through
S-waves (Shear/Secondary waves)  half the P-wave speed
High-frequency, short transverse waves move only through solids
Ground is moved upward and downward as the wave passes through

40. Measuring Earthquakes
Surface Seismic Waves include Love and Rayleigh waves
Love waves vibrate the ground horizontally – A kind of ‘swaying’ motion is felt at the surface
Rayleigh waves are the slowest of all seismic waves – the ground moves up and down in response to Rayleigh wave
Measuring Earthquakes
Instruments are used to record the magnitude of energy released as well as the intensity of shaking by earthquakes
Seismographic equipment measures ground motion as a function of time
Two basic methods of measuring earthquakes are:
Richter’s Magnitude Scale: quantitative, objective, 1 – 10
Mercalli’s Intensity Scale: qualitative, subjective, I - XII

41. Where Do Earthquakes Occur?
Most earthquakes occur in linear belts, along tectonic plate boundaries
80% occur around the Pacific Ocean Basin (along the Pacific Ring of Fire)
Global Distribution of Magnitude 4.5+ Earthquake Activity,

42. Rupture zones along the San Andreas Fault for each of the three major earthquakes:
January 1857 Fort Tejon ▪ April 1906 San Francisco;
October 1989 Loma Prieta

43. NORTHRIDGE EARTHQUAKE, 1994
January 17, :31 a.m. 6.7 on Richter Scale
Earthquake occurred on a blind thrust reverse fault (Oak Ridge Thrust Fault system) and produced the strongest ground motions ever recorded in North America

45. Past Earthquakes
in Southern California

47. CONSEQUENCES OF EARTHQUAKES
Displacement on either side of fault
Vertical and horizontal displacement on Earth’s surface
Seiches
Movement in an enclosed body of water due to intense shaking – Water may actually ‘slosh out’ of the bay or lagoon
Liquefaction
Groundwater rises to surface and destabilizes soils – buildings collapse
Tsunami
Seismic sea wave generated by earthquake on ocean floor

48. Tsunami