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Hiraga Lab
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A lab that synthesizes artificial rocks and deforms them to probe the Earth's interior.
AboutAbout the lab
Understanding rocks from the atomic level.
The Hiraga Lab studies the Earth as a mixture of solid and liquid, and as rock made up of aggregated mineral grains.
In the laboratory, the lab synthesizes rocks and analyzes their structure and chemical composition, especially at the nanoscale.
By combining deformation experiments, high-temperature creep experiments, theoretical modeling, and electron microscope observation, the lab investigates phenomena that occur inside the Earth.
The lab has accepted students from a variety of fields, including seismology and petrology, and also welcomes students who have studied materials science.
Key terms
- Polycrystal
- A solid made up of many small crystal grains. Rock is one kind of polycrystal.
- Creep
- A phenomenon in which a solid slowly deforms when a force is applied continuously at high temperature.
- Diffusion
- The gradual movement of atoms through a material. It is one of the mechanisms by which solids slowly deform.
NewsLab news
Paper published in Journal of Geophysical Research: Solid Earth
A doctoral student received an Outstanding Student Presentation Award at JpGU 2025
ResearchResearch themes
To understand the Earth as a composite of solid and liquid, and as a polycrystalline aggregate of minerals (rock), the lab uses analog deformation experiments, theoretical modeling, high-temperature creep experiments, chemical analysis, and a range of microstructural analysis methods. From the core to the crust, it experimentally investigates diverse phenomena involving the boundaries between grains in rock.
*Illustrative imageMaking Artificial Rocks for Experiments
To reproduce phenomena inside the Earth in the laboratory, the lab developed, with the cooperation of institutions such as the National Institute for Materials Science, a method for making polycrystals (artificial rock samples) that combine various minerals. It can produce samples that are free of cracks, have very little pore space, and have grains finer than 1 micron.
*Illustrative imageHow Resistant Plagioclase Rock Is to Flow
The lab synthesized polycrystals of plagioclase, a mineral of the crust, and determined the flow law for diffusion creep under dry conditions from creep experiments. It showed that plagioclase rock is very stiff, and that the lower crust is not dry.
*Illustrative imageOlivine Grain Shape and Crystal Orientation
In olivine polycrystals, experiments showed that grain shape changes with temperature and time, and that the way crystal orientations align changes accordingly. The lab aims to read the mantle's viscosity and anisotropy from changes in grain shape.
*Illustrative imageGrain Growth and Creep Share the Same Mechanism
In polycrystals made of two kinds of minerals, experiments confirmed that the rate of grain growth and the rate of creep are both governed by the same grain boundary diffusion. This leads to a method for determining the viscosity of rock from grain size and time.
MembersFaculty
The members of the Hiraga Lab consist of faculty, doctoral students, and master's students.As of 2026
- ProfessorTakehiko HiragaPublications ↗
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Wherlite” Strekeisen / CC BY-SA 4.0 (cropped)
- Making Artificial Rocks for Experiments: “Dense pellet forming9” Dominik Bejma, Marta Kowalkińska / CC BY-SA 4.0 (cropped)
- How Resistant Plagioclase Rock Is to Flow: “Labradorescent plagioclase feldspar (Marcy Anorthosite, Mesoproterozoic, 1.16 Ga; Route 3 roadcut south of Bartlett Pond, New York State, USA) 1” James St. John / CC BY 2.0 (cropped)
- Olivine Grain Shape and Crystal Orientation: “Forsterite-Olivine-4jg58d” Robert M. Lavinsky / CC BY-SA 3.0 (cropped)
- Grain Growth and Creep Share the Same Mechanism: “Peridotite mantle xenolith in phonotephrite (Peridot Mesa Flow, Middle Pleistocene, 580 ka; Peridot Mesa, San Carlos Volcanic Field, Arizona, USA) 26” James St. John / CC BY 2.0 (cropped)
- Related lab (Araya Lab): “Interferenz-michelson” FL0 / CC BY-SA 3.0 (cropped)
- Related lab (Mochizuki Lab (Marine Seismology)): “Test des sismomètres OBS (Ocean Bottom Seismometer) en bassin d'essais (Ifremer )” Olivier Dugornay (Ifremer) / CC BY 4.0 (cropped)
- Related lab (Nakatani Lab): “Fault slickenside (Great Smoky Mountains, Tennessee-North Carolina, USA) 1” James St. John / CC BY 2.0 (cropped)
- Related lab (Takei Lab): “Olivine in polarizing light” Islam90 / CC BY-SA 4.0 (cropped)
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