Tharsis Bulge

Formation and Structure

The Tharsis Bulge is a massive volcanic plateau on Mars, formed by a mantle plume that generated vast quantities of basaltic magma. This magma accumulated over billions of years, creating the largest volcanic region in the Solar System. The bulge is approximately the size of a continent and rises about eleven kilometers above the surrounding plains, making it three times higher than the Tibetan plateau. This immense geological feature has significantly influenced the planet’s surface and internal structure.

Geological Features – Volcanoes

The Tharsis Bulge is home to some of the tallest and most significant volcanoes in the Solar System, including:

  • Olympus Mons: The tallest volcano, standing over 22 kilometers high, three times the height of Mount Everest. Olympus Mons is a shield volcano with a diameter of about 600 kilometers, making it one of the largest volcanoes by area as well.
  • Ascraeus Mons: The northernmost of the Tharsis Montes, Ascraeus Mons is about 18 kilometers high. It features a broad, gently sloping shield and is characterized by extensive lava flows and a large caldera at its summit.
  • Pavonis Mons: Located between Ascraeus Mons and Arsia Mons, Pavonis Mons rises to about 14 kilometers. It is notable for its central location in the Tharsis Montes and its well-defined caldera.
  • Arsia Mons: The southernmost and second tallest of the Tharsis Montes, Arsia Mons stands approximately 17 kilometers high. It has a prominent caldera and is known for its extensive system of lava tubes and lava flows.
  • Alba Mons: Formerly known as Alba Patera, this low-profile volcano is located to the north of the Tharsis Montes. Alba Mons is one of the largest volcanoes in the Solar System by area, though it only rises about 6.8 kilometers above the surrounding terrain. It is characterized by gentle slopes and vast lava plains.
  • Uranius Mons: A smaller volcano located northeast of Alba Mons, Uranius Mons rises about 4 kilometers and is part of the larger Uranius Patera volcanic region.
  • Ceraunius Tholus: A smaller shield volcano north of Alba Mons, with a height of about 5.5 kilometers. It has a prominent caldera and is surrounded by other volcanic features.
  • Tharsis Tholus: A moderately high shield volcano located southeast of Alba Mons, Tharsis Tholus stands about 8 kilometers tall. It has a collapsed caldera and is noted for its distinct lava flows.
  • Biblis Tholus: A small volcanic feature southwest of the Tharsis Montes, Biblis Tholus reaches about 3 kilometers in height and is characterized by a central caldera.
  • Ulysses Patera: Located to the west of the Tharsis region, Ulysses Patera is a low, irregularly shaped volcanic feature with an elevation of about 2 kilometers.

Valles Marineris and Radial Fissures

  • Valles Marineris: A vast system of canyons and gorges, stretching over 4,000 kilometers, created by the tectonic stresses associated with the Tharsis Bulge. It is the longest canyon in the Solar System, comparable in length to the width of the United States.
  • Radial Fissures: The formation of the Tharsis Bulge caused the crust to crack, creating a network of radial fissures that extend across the hemisphere.

Meteorite Impacts and Geological History

  • Hellas Basin and Daedalia Planum: Between three and four billion years ago, massive meteorite impacts formed the 2,000-kilometer-wide Hellas Basin and the 4,500-kilometer-wide Daedalia Planum. These impacts contributed to the early geological history of Mars and played a role in shaping the Tharsis region.
  • Continued Volcanism: The Tharsis Bulge has been a site of continuous volcanic activity throughout Mars’s history, from the Noachian period to the present. This activity has resulted in extensive lava flows and the formation of large volcanic plains.

Physical Characteristics

  • Size and Height: The Tharsis Bulge covers a vast area, with its highest points reaching up to 11 kilometers above the surrounding plains. It significantly influences the topography of Mars.
  • Composition: The bulge is composed primarily of basaltic rock, resulting from prolonged volcanic activity. The presence of iron(III) oxide gives the region its reddish appearance.
  • Impact on Mars’s Rotation: The immense mass of the Tharsis Bulge has affected Mars’s moment of inertia, contributing to the planet’s overall rotational dynamics.

Climatic Influence

  • Seasonal Changes: The Tharsis Bulge influences Mars’s climate, contributing to large seasonal changes in the polar ice caps’ coverage. The presence of the bulge affects atmospheric circulation patterns and weather phenomena such as dust storms and devils.
  • Temperature Variations: The high elevation and volcanic activity in the Tharsis region result in significant temperature variations, contributing to the overall climatic dynamics of Mars.

Exploration and Observation

  • Historical Mapping: The Tharsis Bulge was first identified through telescopic observations in the 19th century. Modern spacecraft have provided detailed imagery and data, enhancing our understanding of the region.
  • Scientific Missions: Various missions, including Mariner 9, Viking, Mars Global Surveyor, and Mars Reconnaissance Orbiter, have studied the Tharsis Bulge extensively. These missions have provided insights into the region’s topography, geology, and volcanic history.
  • Current Research: Ongoing research aims to understand the Tharsis Bulge’s formation mechanisms, volcanic activity, and its impact on Mars’s geological evolution.


The Tharsis Bulge is a prominent geological feature on Mars, formed by a mantle plume that produced vast quantities of basaltic magma. This massive volcanic plateau is home to some of the tallest volcanoes in the Solar System, including Olympus Mons, Ascraeus Mons, Pavonis Mons, Arsia Mons, Alba Mons, and other significant volcanic features such as Uranius Mons, Ceraunius Tholus, Tharsis Tholus, Biblis Tholus, and Ulysses Patera. The formation of the Tharsis Bulge has significantly influenced Mars’s surface and internal structure, leading to the creation of radial fissures, Valles Marineris, and extensive volcanic plains. The region’s continuous volcanic activity, coupled with its immense size and height, has played a crucial role in shaping Mars’s topography and climate. Ongoing exploration and research continue to uncover new insights into the Tharsis Bulge, making it a key area of interest for understanding the geological history of Mars.