Dr. Laurie Brown, Geophysicist and Paleomagnetist

Dr. Laurie Brown getting ready to drill a 2.5 million year old lava flow in southern Patagonia, Argentina.

How did you become interested in science?

I always enjoyed the outdoors, growing up outside a small town in upstate New York.  Camping trips with my family took me to many national parks and the wonders of the Western US.  In 8th grade I had a great Earth Science course, which I loved, but I somehow did not connect it as a career path.  I went off the Middlebury College in Vermont to enjoy the mountains and skiing, but majored in Math because it was easy for me.  By Senior year I decided to take a Geology course as an elective (because I liked mountains) and by the second week I was hooked!  It was initially the idea of working outdoors in wild and scenic places that attracted me, but I soon learned there were wonderful scientific problems aplenty.  It was 1968 (yes, I am of that generation!) and the concept of Plate Tectonics was just emerging.  Luckily, I had a wonderful professor teaching the year sequence of Physical and Historical Geology and he brought into class the latest scientific discoveries and made the course exciting and provocative.  He also encouraged me to go to Grad School with my one year of Geology, but lots of Math, Physics, and Chemistry, and the rest is history!

What do you do?

I have been a University professor for 45 years, the last 5 as Emeritus.  Being a professor at a major research university means you do many things, all at the same time!  I taught courses in Geophysics at the undergrad and grad level, as well as other courses needed by my department including Oceanography, Field Methods, Field Mapping, Physical Geology, and Tectonophysics.  I mentored students at all levels, both those in my classes and those working in my lab.  I ran a research program including Masters and PhD students where we worked together both in the field and in my paleomagnetism laboratory.  And, as is common in academia, I did a considerable amount of service for my department, my university, and my profession.

Paleomagnetic cores from Patagonia, cut and labeled, and ready to be measured!

What is your research?

I study the Earth’s magnetic field as it is recorded in earth materials- the field of paleomagnetism.  When rocks form – igneous, sedimentary or metamorphic –they are able to retain a record of the current magnetic field within magnetic minerals (magnetite and hematite primarily) in the rock.  Samples can be collected from these rocks millions of years later and the original field measured for both direction and magnitude.

Field aspects of my research involve collecting oriented samples from in situ outcrops and locations.  Currently I work mostly with hard rocks, both young volcanic flows and ancient metamorphic rocks.  I drill samples from these units using an adapted chain saw with a 1 inch diamond bit, water-cooled to preserve the diamonds.  Usually 8-10 cores are drilled at each site (lava flow or outcrop) and all are oriented in place with a sun compass.  This produces many samples; my current project in southern Patagonia involves 120 separate lava flows, and over 1000 cores!  Paleomagnetic studies also can be done on sedimentary rocks, also drilled in the field, and on lake and ocean cores, where samples are collected from the sediment once the cores are split open.

Measuring basalt cores on the cryongenic magnetometer in the Paleomagnetic Lab at the University of Massachusetts Amherst.

Laboratory measurements are performed on a cryogenic magnetometer in my Paleomagnetism Laboratory here at UMass.  It only takes a few minutes to measure the magnetization in a single sample, but a number of tests for stability and reproducibility are required before the data can be interpreted.  Samples are demagnetized in a step-wise fashion using either high temperatures (up to 700°C) or alternating magnetic fields.  We often measure other magnetic properties of the samples, including magnetic susceptibility (measured both in the field and on lab samples) and hysteresis properties.  Microscopic work or SEM studies help us to identify the carriers of the magnetization.

Current Projects.  I am working at both ends of Earth history as current projects include a major study of paleomagnetic directions from young (< 10 myrs) lava flows from southern South America.  These rocks are being used to investigate how the Earth ’s magnetic field varies in the Southern Hemisphere over the last 10 million years.  Other projects are looking at very old rocks in northern Canada where I study the variations in magnetization in a piece of ancient lower crust, now exposed at the surface, and studies of 900 million year old intrusive rocks in southern Norway that are helping us reconstruct the Earth at a time when all the continents were together in a supercontinent called Rodinia.

Magnetic susceptibility meter on a 1.8 billion year old dike intruding 2.2 billion year old metamorphic rocks, Athabasca Granulite Terrane, northern Canada.

How does your research contribute to climate change and evolution?

Paleomagnetism is able to contribute to studies of climate change, evolution, and the history of the Earth by providing additional methods to both correlate sequences and unconnected outcrops, and by providing additional information on geologic age.  The geomagnetic time scale of normal and reversed polarities is well established, and using this magnetostratigraphy enables us to date sedimentary sequences, and to identify similar sequences in other locations.  Measuring the paleomagnetism of deep-sea cores is so well established that the large drilling ships have on-board magnetic laboratories.  Although I am not doing this kind of magnetic work at present, many other labs are, providing important constraints on the timing and correlation of climatic proxies and many parts of the fossil record.

What is your advice for aspiring scientists?

Persevere!  Find that special part of geoscience that intrigues you and work hard to be the best you can at it.  Take all the various opportunities that are available to you, and see where you go!  There will be ups and downs, but as a career the Geosciences provide many positive and productive possibilities.  With over 50 years of activity in the Geosciences, I can easily say I have never lost my joy of working with and on the Earth and the many interesting problems and challenges it provides.  You, alone, may not solve all the problems facing our planet, but you will greatly contribute to our knowledge of the Earth – its evolution, its history, and its constantly changing environment.  And, along the way, you will interact with a number of other awesome scientists, get to see much of the world, and provide a rewarding and enjoyable career for yourself.

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